{"id":2233214,"url":"http://patchwork.ozlabs.org/api/1.1/patches/2233214/?format=json","web_url":"http://patchwork.ozlabs.org/project/qemu-devel/patch/20260505202640.1011006-2-peterx@redhat.com/","project":{"id":14,"url":"http://patchwork.ozlabs.org/api/1.1/projects/14/?format=json","name":"QEMU Development","link_name":"qemu-devel","list_id":"qemu-devel.nongnu.org","list_email":"qemu-devel@nongnu.org","web_url":"","scm_url":"","webscm_url":""},"msgid":"<20260505202640.1011006-2-peterx@redhat.com>","date":"2026-05-05T20:26:18","name":"[PULL,01/23] migration: Fix blocking in POSTCOPY_DEVICE during package load","commit_ref":null,"pull_url":null,"state":"new","archived":false,"hash":"3ce377ff7b07ba5a13ad54bba32a3ec7b20da7bf","submitter":{"id":67717,"url":"http://patchwork.ozlabs.org/api/1.1/people/67717/?format=json","name":"Peter Xu","email":"peterx@redhat.com"},"delegate":null,"mbox":"http://patchwork.ozlabs.org/project/qemu-devel/patch/20260505202640.1011006-2-peterx@redhat.com/mbox/","series":[{"id":502897,"url":"http://patchwork.ozlabs.org/api/1.1/series/502897/?format=json","web_url":"http://patchwork.ozlabs.org/project/qemu-devel/list/?series=502897","date":"2026-05-05T20:26:17","name":"[PULL,01/23] migration: Fix blocking in POSTCOPY_DEVICE during package load","version":1,"mbox":"http://patchwork.ozlabs.org/series/502897/mbox/"}],"comments":"http://patchwork.ozlabs.org/api/patches/2233214/comments/","check":"pending","checks":"http://patchwork.ozlabs.org/api/patches/2233214/checks/","tags":{},"headers":{"Return-Path":"","X-Original-To":"incoming@patchwork.ozlabs.org","Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (1024-bit key;\n unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256\n header.s=mimecast20190719 header.b=RY2cdt8G;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256\n header.s=google header.b=mG2GN8G6;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=nongnu.org\n (client-ip=209.51.188.17; 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envelope-from=peterx@redhat.com;\n helo=us-smtp-delivery-124.mimecast.com","X-Spam_score_int":"-24","X-Spam_score":"-2.5","X-Spam_bar":"--","X-Spam_report":"(-2.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.443,\n DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1,\n RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001,\n SPF_HELO_PASS=-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":"qemu development ","List-Unsubscribe":",\n ","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n ","Errors-To":"qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org","Sender":"qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org"},"content":"From: Pranav Tyagi \n\nThe package_loaded event is not set in case MIG_RP_MSG_PONG does not\narrive on the source from the destination in the return path thread. The\nmigration thread would then be blocked waiting for package_loaded event\nindefinitely in POSTCOPY_DEVICE state. Where as, in such a condition the\nsource VM can safely resume as the destination has not yet started. The\npong message can get lost in case of a network failure or destination\ncrash before sending the pong.\n\nThis patch removes the package_loaded event and uses rp_sem, instead of\nkicking multiple events. The error is detected in case of network\nfailure or destination crash and rp_sem is set in the out path of the\nreturn path thread. This will kick the migration thread out from a\ncondition of indefinitely waiting for rp_sem. The migration thread then\nfails early and breaks from the migration loop to resume the vm on the\nsource side.\n\nFixes: 7b842fe354c6 (\"migration: Introduce POSTCOPY_DEVICE state\")\nSigned-off-by: Pranav Tyagi \nReviewed-by: Juraj Marcin \nReviewed-by: Peter Xu \nLink: https://lore.kernel.org/r/20260423094438.43556-1-prtyagi@redhat.com\nSigned-off-by: Peter Xu \n---\n migration/migration.h | 1 -\n migration/migration.c | 48 ++++++++++++++++++++++++++++---------------\n 2 files changed, 31 insertions(+), 18 deletions(-)","diff":"diff --git a/migration/migration.h b/migration/migration.h\nindex b6888daced..9081e6a612 100644\n--- a/migration/migration.h\n+++ b/migration/migration.h\n@@ -512,7 +512,6 @@ struct MigrationState {\n bool rdma_migration;\n \n bool postcopy_package_loaded;\n- QemuEvent postcopy_package_loaded_event;\n \n GSource *hup_source;\n \ndiff --git a/migration/migration.c b/migration/migration.c\nindex 5c9aaa6e58..6e4988a590 100644\n--- a/migration/migration.c\n+++ b/migration/migration.c\n@@ -1661,7 +1661,6 @@ int migrate_init(MigrationState *s, Error **errp)\n migration_reset_vfio_bytes_transferred();\n \n s->postcopy_package_loaded = false;\n- qemu_event_reset(&s->postcopy_package_loaded_event);\n \n return 0;\n }\n@@ -2317,7 +2316,7 @@ static void *source_return_path_thread(void *opaque)\n if (tmp32 == QEMU_VM_PING_PACKAGED_LOADED) {\n trace_source_return_path_thread_postcopy_package_loaded();\n ms->postcopy_package_loaded = true;\n- qemu_event_set(&ms->postcopy_package_loaded_event);\n+ migration_rp_kick(ms);\n }\n break;\n \n@@ -2388,16 +2387,21 @@ out:\n trace_source_return_path_thread_bad_end();\n }\n \n- if (ms->state == MIGRATION_STATUS_POSTCOPY_RECOVER) {\n+ if (ms->state == MIGRATION_STATUS_POSTCOPY_RECOVER ||\n+ ms->state == MIGRATION_STATUS_POSTCOPY_DEVICE) {\n /*\n- * this will be extremely unlikely: that we got yet another network\n- * issue during recovering of the 1st network failure.. during this\n- * period the main migration thread can be waiting on rp_sem for\n- * this thread to sync with the other side.\n+ * The migration thread can get stuck waiting for rp_sem if the\n+ * return path fails to sync with the destination. This handles\n+ * two specific cases:\n *\n- * When this happens, explicitly kick the migration thread out of\n- * RECOVER stage and back to PAUSED, so the admin can try\n- * everything again.\n+ * POSTCOPY_RECOVER: A failure occurs during a recovery attempt.\n+ * We kick the migration thread back to PAUSED so the admin can\n+ * retry.\n+ *\n+ * POSTCOPY_DEVICE: The MIG_RP_MSG_PONG is lost due to a\n+ * network failure or destination crash. We kick the migration\n+ * thread out of its wait so it can fail the migration and safely\n+ * resume the VM on the source.\n */\n migration_rp_kick(ms);\n }\n@@ -3226,12 +3230,24 @@ static MigIterateState migration_iteration_run(MigrationState *s)\n if (s->state == MIGRATION_STATUS_POSTCOPY_DEVICE &&\n (s->postcopy_package_loaded || complete_ready)) {\n /*\n- * If package has been loaded, the event is set and we will\n- * immediatelly transition to POSTCOPY_ACTIVE. If we are ready for\n- * completion, we need to wait for destination to load the postcopy\n- * package before actually completing.\n+ * We will immediately transition to POSTCOPY_ACTIVE.\n+ * If we are ready for completion, we need to wait for\n+ * destination to load the postcopy package before actually\n+ * completing.\n */\n- qemu_event_wait(&s->postcopy_package_loaded_event);\n+ while (!s->postcopy_package_loaded) {\n+ if (migration_rp_wait(s)) {\n+ /*\n+ * Error happened. Migration thread was stuck waiting in\n+ * POSTCOPY_DEVICE for rp_sem which was never set.\n+ */\n+ migrate_set_state(&s->state,\n+ MIGRATION_STATUS_POSTCOPY_DEVICE,\n+ MIGRATION_STATUS_FAILING);\n+ return MIG_ITERATE_BREAK;\n+ }\n+ }\n+ /* Acknowledgement received from the destination */\n migrate_set_state(&s->state, MIGRATION_STATUS_POSTCOPY_DEVICE,\n MIGRATION_STATUS_POSTCOPY_ACTIVE);\n }\n@@ -3863,7 +3879,6 @@ static void migration_instance_finalize(Object *obj)\n qemu_sem_destroy(&ms->rp_state.rp_pong_acks);\n qemu_sem_destroy(&ms->postcopy_qemufile_src_sem);\n error_free(ms->error);\n- qemu_event_destroy(&ms->postcopy_package_loaded_event);\n }\n \n static void migration_instance_init(Object *obj)\n@@ -3885,7 +3900,6 @@ static void migration_instance_init(Object *obj)\n qemu_sem_init(&ms->wait_unplug_sem, 0);\n qemu_sem_init(&ms->postcopy_qemufile_src_sem, 0);\n qemu_mutex_init(&ms->qemu_file_lock);\n- qemu_event_init(&ms->postcopy_package_loaded_event, 0);\n }\n \n /*\n","prefixes":["PULL","01/23"]}