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([2a01:e0a:280:24f0:9db0:474c:ff43:9f5c]) by smtp.gmail.com with ESMTPSA id ia21-20020a0561024b1500b0047065173094sm224148vsb.1.2024.02.29.05.34.47 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 29 Feb 2024 05:34:49 -0800 (PST) Message-ID: <356b2acd-cdbd-4517-a4e0-624f9b9484cc@redhat.com> Date: Thu, 29 Feb 2024 14:34:27 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 06/21] migration: Add Error** argument to .save_setup() handler Content-Language: en-US, fr To: Markus Armbruster Cc: qemu-devel@nongnu.org, Peter Xu , Fabiano Rosas , Alex Williamson , Avihai Horon , =?UTF-8?Q?Philippe_Mathieu-Daud=C3=A9?= , Nicholas Piggin , Harsh Prateek Bora , Halil Pasic , Thomas Huth , Eric Blake , Vladimir Sementsov-Ogievskiy , John Snow , Stefan Hajnoczi References: <20240227180345.548960-1-clg@redhat.com> <20240227180345.548960-7-clg@redhat.com> <87zfvj3hnd.fsf@pond.sub.org> From: =?UTF-8?Q?C=C3=A9dric_Le_Goater?= In-Reply-To: <87zfvj3hnd.fsf@pond.sub.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=170.10.133.124; envelope-from=clg@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=-0.096, 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_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, 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 On 2/29/24 07:32, Markus Armbruster wrote: > Cédric 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-Daudé >> Reviewed-by: Peter Xu >> Signed-off-by: Cédric Le Goater >> --- > > [...] > >> diff --git a/hw/s390x/s390-stattrib.c b/hw/s390x/s390-stattrib.c >> index c483b62a9b5f71772639fc180bdad15ecb6711cb..c934df424a555d83d2198f5ddfc0cbe0ea98e9ec 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 version_id) >> return ret; >> } >> >> -static int cmma_save_setup(QEMUFile *f, void *opaque) >> +static int cmma_save_setup(QEMUFile *f, void *opaque, Error **errp) >> { >> S390StAttribState *sas = S390_STATTRIB(opaque); >> S390StAttribClass *sac = S390_STATTRIB_GET_CLASS(sas); > int res; > /* > * Signal that we want to start a migration, thus needing PGSTE dirty > * tracking. > */ > res = 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 > * • bool-valued functions return true on success / false on failure, > * • pointer-valued functions return non-null / null pointer, and > * • 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. Indeed. I will check the other changes. > Questions? Perfectly clear. Thanks, C.