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Tsirkin" , Marcel Apfelbaum , Peter Xu , Fabiano Rosas , Steve Sistare Subject: [PATCH V2 27/45] migration: cpr_get_fd_param helper Date: Fri, 14 Feb 2025 06:14:09 -0800 Message-Id: <1739542467-226739-28-git-send-email-steven.sistare@oracle.com> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1739542467-226739-1-git-send-email-steven.sistare@oracle.com> References: <1739542467-226739-1-git-send-email-steven.sistare@oracle.com> X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1057,Hydra:6.0.680,FMLib:17.12.68.34 definitions=2025-02-14_06,2025-02-13_01,2024-11-22_01 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 mlxlogscore=999 phishscore=0 malwarescore=0 mlxscore=0 spamscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2501170000 definitions=main-2502140104 X-Proofpoint-ORIG-GUID: swOtxUWr5BrwHFzqZuKiNheOFV1v5YXh X-Proofpoint-GUID: swOtxUWr5BrwHFzqZuKiNheOFV1v5YXh Received-SPF: pass client-ip=205.220.165.32; envelope-from=steven.sistare@oracle.com; helo=mx0a-00069f02.pphosted.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 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_H2=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_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 --- include/migration/cpr.h | 2 ++ migration/cpr.c | 40 ++++++++++++++++++++++++++++++++++++++++ 2 files changed, 42 insertions(+) diff --git a/include/migration/cpr.h b/include/migration/cpr.h index c5c191d..23d0af4 100644 --- a/include/migration/cpr.h +++ b/include/migration/cpr.h @@ -33,6 +33,8 @@ struct QIOChannel *cpr_state_ioc(void); bool cpr_needed_for_reuse(void *opaque); void cpr_kvm_close(void); +int cpr_get_fd_param(const char *name, const char *fdname, int index, + bool *reused, Error **errp); void cpr_transfer_init(void); QEMUFile *cpr_transfer_output(MigrationChannel *channel, Error **errp); diff --git a/migration/cpr.c b/migration/cpr.c index 351e12d..c903b24 100644 --- a/migration/cpr.c +++ b/migration/cpr.c @@ -14,6 +14,7 @@ #include "migration/qemu-file.h" #include "migration/savevm.h" #include "migration/vmstate.h" +#include "monitor/monitor.h" #include "system/kvm.h" #include "system/runstate.h" #include "trace.h" @@ -274,3 +275,42 @@ void cpr_kvm_close(void) kvm_close(); vfio_kvm_device_close(); } + +/* + * 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 + * @reused: returns true if the fd is found in CPR state, else false. + * @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, + bool *reused, 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); + } + *reused = true; + } 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); + } + *reused = false; + } + return fd; +}