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[109.43.178.133]) by smtp.gmail.com with ESMTPSA id r13-20020ac85e8d000000b0042e703a8d74sm574557qtx.56.2024.02.29.02.35.45 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 29 Feb 2024 02:35:49 -0800 (PST) Message-ID: Date: Thu, 29 Feb 2024 11:35:44 +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 To: Vladimir Sementsov-Ogievskiy , Markus Armbruster , =?UTF-8?Q?C=C3=A9dric_Le_Goater?= 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 , Eric Blake , John Snow , Stefan Hajnoczi References: <20240227180345.548960-1-clg@redhat.com> <20240227180345.548960-7-clg@redhat.com> <87zfvj3hnd.fsf@pond.sub.org> <86d70a2e-7250-440b-bcd6-7877fe3b3dba@yandex-team.ru> From: Thomas Huth Autocrypt: addr=thuth@redhat.com; keydata= xsFNBFH7eUwBEACzyOXKU+5Pcs6wNpKzrlJwzRl3VGZt95VCdb+FgoU9g11m7FWcOafrVRwU yYkTm9+7zBUc0sW5AuPGR/dp3pSLX/yFWsA/UB4nJsHqgDvDU7BImSeiTrnpMOTXb7Arw2a2 4CflIyFqjCpfDM4MuTmzTjXq4Uov1giGE9X6viNo1pxyEpd7PanlKNnf4PqEQp06X4IgUacW tSGj6Gcns1bCuHV8OPWLkf4hkRnu8hdL6i60Yxz4E6TqlrpxsfYwLXgEeswPHOA6Mn4Cso9O 0lewVYfFfsmokfAVMKWzOl1Sr0KGI5T9CpmRfAiSHpthhHWnECcJFwl72NTi6kUcUzG4se81 O6n9d/kTj7pzTmBdfwuOZ0YUSqcqs0W+l1NcASSYZQaDoD3/SLk+nqVeCBB4OnYOGhgmIHNW 0CwMRO/GK+20alxzk//V9GmIM2ACElbfF8+Uug3pqiHkVnKqM7W9/S1NH2qmxB6zMiJUHlTH gnVeZX0dgH27mzstcF786uPcdEqS0KJuxh2kk5IvUSL3Qn3ZgmgdxBMyCPciD/1cb7/Ahazr 3ThHQXSHXkH/aDXdfLsKVuwDzHLVSkdSnZdt5HHh75/NFHxwaTlydgfHmFFwodK8y/TjyiGZ zg2Kje38xnz8zKn9iesFBCcONXS7txENTzX0z80WKBhK+XSFJwARAQABzR5UaG9tYXMgSHV0 aCA8dGh1dGhAcmVkaGF0LmNvbT7CwXgEEwECACIFAlVgX6oCGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAAoJEC7Z13T+cC21EbIP/ii9cvT2HHGbFRl8HqGT6+7Wkb+XLMqJBMAIGiQK QIP3xk1HPTsLfVG0ao4hy/oYkGNOP8+ubLnZen6Yq3zAFiMhQ44lvgigDYJo3Ve59gfe99KX EbtB+X95ODARkq0McR6OAsPNJ7gpEUzfkQUUJTXRDQXfG/FX303Gvk+YU0spm2tsIKPl6AmV 1CegDljzjycyfJbk418MQmMu2T82kjrkEofUO2a24ed3VGC0/Uz//XCR2ZTo+vBoBUQl41BD eFFtoCSrzo3yPFS+w5fkH9NT8ChdpSlbNS32NhYQhJtr9zjWyFRf0Zk+T/1P7ECn6gTEkp5k ofFIA4MFBc/fXbaDRtBmPB0N9pqTFApIUI4vuFPPO0JDrII9dLwZ6lO9EKiwuVlvr1wwzsgq zJTPBU3qHaUO4d/8G+gD7AL/6T4zi8Jo/GmjBsnYaTzbm94lf0CjXjsOX3seMhaE6WAZOQQG tZHAO1kAPWpaxne+wtgMKthyPLNwelLf+xzGvrIKvLX6QuLoWMnWldu22z2ICVnLQChlR9d6 WW8QFEpo/FK7omuS8KvvopFcOOdlbFMM8Y/8vBgVMSsK6fsYUhruny/PahprPbYGiNIhKqz7 UvgyZVl4pBFjTaz/SbimTk210vIlkDyy1WuS8Zsn0htv4+jQPgo9rqFE4mipJjy/iboDzsFN BFH7eUwBEAC2nzfUeeI8dv0C4qrfCPze6NkryUflEut9WwHhfXCLjtvCjnoGqFelH/PE9NF4 4VPSCdvD1SSmFVzu6T9qWdcwMSaC+e7G/z0/AhBfqTeosAF5XvKQlAb9ZPkdDr7YN0a1XDfa +NgA+JZB4ROyBZFFAwNHT+HCnyzy0v9Sh3BgJJwfpXHH2l3LfncvV8rgFv0bvdr70U+On2XH 5bApOyW1WpIG5KPJlDdzcQTyptOJ1dnEHfwnABEfzI3dNf63rlxsGouX/NFRRRNqkdClQR3K gCwciaXfZ7ir7fF0u1N2UuLsWA8Ei1JrNypk+MRxhbvdQC4tyZCZ8mVDk+QOK6pyK2f4rMf/ WmqxNTtAVmNuZIwnJdjRMMSs4W4w6N/bRvpqtykSqx7VXcgqtv6eqoDZrNuhGbekQA0sAnCJ VPArerAZGArm63o39me/bRUQeQVSxEBmg66yshF9HkcUPGVeC4B0TPwz+HFcVhheo6hoJjLq knFOPLRj+0h+ZL+D0GenyqD3CyuyeTT5dGcNU9qT74bdSr20k/CklvI7S9yoQje8BeQAHtdV cvO8XCLrpGuw9SgOS7OP5oI26a0548M4KldAY+kqX6XVphEw3/6U1KTf7WxW5zYLTtadjISB X9xsRWSU+Yqs3C7oN5TIPSoj9tXMoxZkCIHWvnqGwZ7JhwARAQABwsFfBBgBAgAJBQJR+3lM AhsMAAoJEC7Z13T+cC21hPAQAIsBL9MdGpdEpvXs9CYrBkd6tS9mbaSWj6XBDfA1AEdQkBOn ZH1Qt7HJesk+qNSnLv6+jP4VwqK5AFMrKJ6IjE7jqgzGxtcZnvSjeDGPF1h2CKZQPpTw890k fy18AvgFHkVk2Oylyexw3aOBsXg6ukN44vIFqPoc+YSU0+0QIdYJp/XFsgWxnFIMYwDpxSHS 5fdDxUjsk3UBHZx+IhFjs2siVZi5wnHIqM7eK9abr2cK2weInTBwXwqVWjsXZ4tq5+jQrwDK cvxIcwXdUTLGxc4/Z/VRH1PZSvfQxdxMGmNTGaXVNfdFZjm4fz0mz+OUi6AHC4CZpwnsliGV ODqwX8Y1zic9viSTbKS01ZNp175POyWViUk9qisPZB7ypfSIVSEULrL347qY/hm9ahhqmn17 Ng255syASv3ehvX7iwWDfzXbA0/TVaqwa1YIkec+/8miicV0zMP9siRcYQkyTqSzaTFBBmqD oiT+z+/E59qj/EKfyce3sbC9XLjXv3mHMrq1tKX4G7IJGnS989E/fg6crv6NHae9Ckm7+lSs IQu4bBP2GxiRQ+NV3iV/KU3ebMRzqIC//DCOxzQNFNJAKldPe/bKZMCxEqtVoRkuJtNdp/5a yXFZ6TfE1hGKrDBYAm4vrnZ4CXFSBDllL59cFFOJCkn4Xboj/aVxxJxF30bn In-Reply-To: <86d70a2e-7250-440b-bcd6-7877fe3b3dba@yandex-team.ru> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=170.10.133.124; envelope-from=thuth@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, 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 29/02/2024 08.20, Vladimir Sementsov-Ogievskiy wrote: > On 29.02.24 09:32, 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, > > Personally, I'd prefer not doing so. Creating wrong commits and fixing them > in same series - better to merge all fixes into bad commit:) I agree - that might create issues with bisecting later. Please fix it in this patch here already! Thanks, Thomas