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 58553C54E55 for ; Thu, 29 Feb 2024 06:33:40 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1rfZyL-0006J7-8i; Thu, 29 Feb 2024 01:32:50 -0500 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 1rfZy2-0006GP-Et for qemu-devel@nongnu.org; Thu, 29 Feb 2024 01:32:39 -0500 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 1rfZxm-0002Hj-RQ for qemu-devel@nongnu.org; Thu, 29 Feb 2024 01:32:29 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1709188332; 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=/jNDOfAqaSPp1d1AwFGj9q6q/4uUpccuEXmFzFAloFo=; b=Z4SY4X8Dt/Ga/5wAOdOXFuBQvbgl86tJuO921B582+u0E//txBs6uijQWAnzaiX1Ux0aHC P+xMvENuvKSxNooYti0mqLomPGESZCdKiiDQ64FtqWnkbJUbFYiwVC82L2ErGks1hnPhl9 xQNqTFnvN9oJNTVxK5oQVOsCGeVXpoI= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-255-LElognIWN3Sa7vQ3Txqq-w-1; Thu, 29 Feb 2024 01:32:09 -0500 X-MC-Unique: LElognIWN3Sa7vQ3Txqq-w-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (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 mimecast-mx02.redhat.com (Postfix) with ESMTPS id 9D17A85A589; Thu, 29 Feb 2024 06:32:08 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.39.193.4]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 310612166B5E; Thu, 29 Feb 2024 06:32:08 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id D4C8F21E6740; Thu, 29 Feb 2024 07:32:06 +0100 (CET) From: Markus Armbruster To: =?utf-8?Q?C=C3=A9dric?= Le Goater Cc: qemu-devel@nongnu.org, Peter Xu , Fabiano Rosas , Alex Williamson , Avihai Horon , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , Nicholas Piggin , Harsh Prateek Bora , Halil Pasic , Thomas Huth , Eric Blake , Vladimir Sementsov-Ogievskiy , John Snow , Stefan Hajnoczi Subject: Re: [PATCH v2 06/21] migration: Add Error** argument to .save_setup() handler In-Reply-To: <20240227180345.548960-7-clg@redhat.com> (=?utf-8?Q?=22C?= =?utf-8?Q?=C3=A9dric?= Le Goater"'s message of "Tue, 27 Feb 2024 19:03:30 +0100") References: <20240227180345.548960-1-clg@redhat.com> <20240227180345.548960-7-clg@redhat.com> Date: Thu, 29 Feb 2024 07:32:06 +0100 Message-ID: <87zfvj3hnd.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 10.11.54.6 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: -21 X-Spam_score: -2.2 X-Spam_bar: -- X-Spam_report: (-2.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.102, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 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 C=C3=A9dric Le Goater writes: > The purpose is to record a potential error in the migration stream if > qemu_savevm_state_setup() fails. Most of the current .save_setup() > handlers can be modified to use the Error argument instead of managing > their own and calling locally error_report(). The following patches > will introduce such changes for VFIO first. > > Cc: Nicholas Piggin > Cc: Harsh Prateek Bora > Cc: Halil Pasic > Cc: Thomas Huth > Cc: Eric Blake > Cc: Vladimir Sementsov-Ogievskiy > Cc: John Snow > Cc: Stefan Hajnoczi > Reviewed-by: Philippe Mathieu-Daud=C3=A9 > Reviewed-by: Peter Xu > Signed-off-by: C=C3=A9dric Le Goater > --- [...] > diff --git a/hw/s390x/s390-stattrib.c b/hw/s390x/s390-stattrib.c > index c483b62a9b5f71772639fc180bdad15ecb6711cb..c934df424a555d83d2198f5dd= fc0cbe0ea98e9ec 100644 > --- a/hw/s390x/s390-stattrib.c > +++ b/hw/s390x/s390-stattrib.c > @@ -166,7 +166,7 @@ static int cmma_load(QEMUFile *f, void *opaque, int v= ersion_id) > return ret; > } >=20=20 > -static int cmma_save_setup(QEMUFile *f, void *opaque) > +static int cmma_save_setup(QEMUFile *f, void *opaque, Error **errp) > { > S390StAttribState *sas =3D S390_STATTRIB(opaque); > S390StAttribClass *sac =3D S390_STATTRIB_GET_CLASS(sas); int res; /* * Signal that we want to start a migration, thus needing PGSTE dirty * tracking. */ res =3D sac->set_migrationmode(sas, 1); if (res) { return res; I believe this is a failure return. Anti-pattern: fail without setting an error. There might be more elsewhere in the series. qapi/error.h's big comment: * - On success, the function should not touch *errp. On failure, it * should set a new error, e.g. with error_setg(errp, ...), or * propagate an existing one, e.g. with error_propagate(errp, ...). * * - 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. } qemu_put_be64(f, STATTR_FLAG_EOS); return 0; } When adding Error **errp to a function, you must also add code to set an error on failure to every failure path. Adding it in a later patch in the same series can be okay, but I'd add a TODO comment to the function then, and mention it in the commit message. Questions? [...]