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Tsirkin" , Marcel Apfelbaum , Peter Xu , Fabiano Rosas , Steve Sistare Subject: [PATCH V6 04/21] migration: cpr_get_fd_param helper Date: Wed, 2 Jul 2025 14:58:41 -0700 Message-Id: <1751493538-202042-5-git-send-email-steven.sistare@oracle.com> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1751493538-202042-1-git-send-email-steven.sistare@oracle.com> References: <1751493538-202042-1-git-send-email-steven.sistare@oracle.com> X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1099,Hydra:6.1.7,FMLib:17.12.80.40 definitions=2025-07-02_04,2025-07-02_04,2025-03-28_01 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 malwarescore=0 spamscore=0 adultscore=0 mlxlogscore=999 phishscore=0 suspectscore=0 mlxscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2505160000 definitions=main-2507020182 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwNzAyMDE4MiBTYWx0ZWRfX/0bxD0jWuAvX MANgzENymiHZVdHIdEiEIriF5ISqRLPPdMBwJar6oi6ATmvDfXX38OChEU3a1S5Xcq/sdzjryMG DQeixpzA++7OPsUyZQCngwKdjsMtHKaqIneoruBKi+xD5LniJkusmBNhfV6D5zSmOEkHmVxMHCw 3uu1i/qI8y7MQew3HhGeI9lNGjI32dug12nsFT/V1QIz+NCPhmurhoa1BolhzJe+1Bfte6IvN6b cZQwDc9jXRVkIFRFvkjIeWXFgd4gqut0do7q9oCy2nFVr3VjWsgj4t/pKxudx5O2AJvIowupJQe k41N3ORaiFkKBjeRByiqGnsCaT+AAfZWaSNaUMKL8x8RZzAYDVHyLywjlSib61x73aem0SkfF5A 01kP9IoFVpT/bXfaC0Xn7+vSLFNlwr67H6cea0WgO+33diow6CwPgEA/lMbqUV/LeJSPLkoo X-Authority-Analysis: v=2.4 cv=LcU86ifi c=1 sm=1 tr=0 ts=6865aba7 cx=c_pps a=OOZaFjgC48PWsiFpTAqLcw==:117 a=OOZaFjgC48PWsiFpTAqLcw==:17 a=Wb1JkmetP80A:10 a=yPCof4ZbAAAA:8 a=xj5pLq7tU-gV2qsf3bMA:9 X-Proofpoint-GUID: YhOfrRgr4FbD6MSTQzx1IhzGCvvl0vJg X-Proofpoint-ORIG-GUID: YhOfrRgr4FbD6MSTQzx1IhzGCvvl0vJg Received-SPF: pass client-ip=205.220.165.32; envelope-from=steven.sistare@oracle.com; helo=mx0a-00069f02.pphosted.com X-Spam_score_int: -25 X-Spam_score: -2.6 X-Spam_bar: -- X-Spam_report: (-2.6 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_MED=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.237, RCVD_IN_VALIDITY_RPBL_BLOCKED=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: 2.1.29 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 Add the helper function cpr_get_fd_param, to use when preserving a file descriptor that is opened externally and passed to QEMU. cpr_get_fd_param returns a descriptor number either from a QEMU command-line parameter, from a getfd command, or from CPR state. When a descriptor is passed to new QEMU via SCM_RIGHTS, its number changes. Hence, during CPR, the command-line parameter is ignored in new QEMU, and over-ridden by the value found in CPR state. Similarly, if the descriptor was originally specified by a getfd command in old QEMU, the fd number is not known outside of QEMU, and it changes when sent to new QEMU via SCM_RIGHTS. Hence the user cannot send getfd to new QEMU, but when the user sends a hotplug command that references the fd, cpr_get_fd_param finds its value in CPR state. Signed-off-by: Steve Sistare Reviewed-by: Fabiano Rosas --- include/migration/cpr.h | 2 ++ migration/cpr.c | 37 +++++++++++++++++++++++++++++++++++++ 2 files changed, 39 insertions(+) diff --git a/include/migration/cpr.h b/include/migration/cpr.h index 07858e9..eb27a93 100644 --- a/include/migration/cpr.h +++ b/include/migration/cpr.h @@ -32,6 +32,8 @@ void cpr_state_close(void); struct QIOChannel *cpr_state_ioc(void); bool cpr_incoming_needed(void *opaque); +int cpr_get_fd_param(const char *name, const char *fdname, int index, + Error **errp); QEMUFile *cpr_transfer_output(MigrationChannel *channel, Error **errp); QEMUFile *cpr_transfer_input(MigrationChannel *channel, Error **errp); diff --git a/migration/cpr.c b/migration/cpr.c index a50a57e..535d587 100644 --- a/migration/cpr.c +++ b/migration/cpr.c @@ -13,6 +13,7 @@ #include "migration/qemu-file.h" #include "migration/savevm.h" #include "migration/vmstate.h" +#include "monitor/monitor.h" #include "system/runstate.h" #include "trace.h" @@ -264,3 +265,39 @@ bool cpr_incoming_needed(void *opaque) MigMode mode = migrate_mode(); return mode == MIG_MODE_CPR_TRANSFER; } + +/* + * cpr_get_fd_param: find a descriptor and return its value. + * + * @name: CPR name for the descriptor + * @fdname: An integer-valued string, or a name passed to a getfd command + * @index: CPR index of the descriptor + * @errp: returned error message + * + * If CPR is not being performed, then use @fdname to find the fd. + * If CPR is being performed, then ignore @fdname, and look for @name + * and @index in CPR state. + * + * On success returns the fd value, else returns -1. + */ +int cpr_get_fd_param(const char *name, const char *fdname, int index, + Error **errp) +{ + ERRP_GUARD(); + int fd; + + if (cpr_is_incoming()) { + fd = cpr_find_fd(name, index); + if (fd < 0) { + error_setg(errp, "cannot find saved value for fd %s", fdname); + } + } else { + fd = monitor_fd_param(monitor_cur(), fdname, errp); + if (fd >= 0) { + cpr_save_fd(name, index, fd); + } else { + error_prepend(errp, "Could not parse object fd %s:", fdname); + } + } + return fd; +} -- 1.8.3.1