qemu: Avoid duplicate resume events and state changes

The only place where VIR_DOMAIN_EVENT_RESUMED should be generated is the
RESUME event handler to make sure we don't generate duplicate events or
state changes. In the worse case the duplicity can revert or cover
changes done by other event handlers.

For example, after QEMU sent RESUME, BLOCK_IO_ERROR, and STOP events
we could happily mark the domain as running and report
VIR_DOMAIN_EVENT_RESUMED to registered clients.

https://bugzilla.redhat.com/show_bug.cgi?id=1612943

Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
Reviewed-by: John Ferlan <jferlan@redhat.com>

src/qemu/qemu_driver.c

@@ -1861,7 +1861,6 @@ static int qemuDomainResume(virDomainPtr dom)
     virQEMUDriverPtr driver = dom->conn->privateData;
     virDomainObjPtr vm;
     int ret = -1;
-    virObjectEventPtr event = NULL;
     int state;
     int reason;
     virQEMUDriverConfigPtr cfg = NULL;
@@ -1900,9 +1899,6 @@ static int qemuDomainResume(virDomainPtr dom)
                                "%s", _("resume operation failed"));
             goto endjob;
         }
-        event = virDomainEventLifecycleNewFromObj(vm,
-                                         VIR_DOMAIN_EVENT_RESUMED,
-                                         VIR_DOMAIN_EVENT_RESUMED_UNPAUSED);
     }
     if (virDomainSaveStatus(driver->xmlopt, cfg->stateDir, vm, driver->caps) < 0)
         goto endjob;
@@ -1913,7 +1909,6 @@ static int qemuDomainResume(virDomainPtr dom)
 
  cleanup:
     virDomainObjEndAPI(&vm);
-    virObjectEventStateQueue(driver->domainEventState, event);
     virObjectUnref(cfg);
     return ret;
 }
@@ -15983,7 +15978,6 @@ qemuDomainRevertToSnapshot(virDomainSnapshotPtr snapshot,
     virDomainDefPtr config = NULL;
     virQEMUDriverConfigPtr cfg = NULL;
     virCapsPtr caps = NULL;
-    bool was_running = false;
     bool was_stopped = false;
     qemuDomainSaveCookiePtr cookie;
     virCPUDefPtr origCPU = NULL;
@@ -16174,7 +16168,6 @@ qemuDomainRevertToSnapshot(virDomainSnapshotPtr snapshot,
             priv = vm->privateData;
             if (virDomainObjGetState(vm, NULL) == VIR_DOMAIN_RUNNING) {
                 /* Transitions 5, 6 */
-                was_running = true;
                 if (qemuProcessStopCPUs(driver, vm,
                                         VIR_DOMAIN_PAUSED_FROM_SNAPSHOT,
                                         QEMU_ASYNC_JOB_START) < 0)
@@ -16271,12 +16264,6 @@ qemuDomainRevertToSnapshot(virDomainSnapshotPtr snapshot,
                 event = virDomainEventLifecycleNewFromObj(vm,
                                                  VIR_DOMAIN_EVENT_STARTED,
                                                  detail);
-            } else if (!was_running) {
-                /* Transition 8 */
-                detail = VIR_DOMAIN_EVENT_RESUMED_FROM_SNAPSHOT;
-                event = virDomainEventLifecycleNewFromObj(vm,
-                                                 VIR_DOMAIN_EVENT_RESUMED,
-                                                 detail);
             }
         }
         break;

src/qemu/qemu_migration.c

@@ -2982,14 +2982,10 @@ qemuMigrationSrcConfirmPhase(virQEMUDriverPtr driver,
         virFreeError(orig_err);
 
         if (virDomainObjGetState(vm, &reason) == VIR_DOMAIN_PAUSED &&
-            reason == VIR_DOMAIN_PAUSED_POSTCOPY) {
+            reason == VIR_DOMAIN_PAUSED_POSTCOPY)
             qemuMigrationAnyPostcopyFailed(driver, vm);
-        } else if (qemuMigrationSrcRestoreDomainState(driver, vm)) {
+        else
-            event = virDomainEventLifecycleNewFromObj(vm,
+            qemuMigrationSrcRestoreDomainState(driver, vm);
-                                                      VIR_DOMAIN_EVENT_RESUMED,
-                                                      VIR_DOMAIN_EVENT_RESUMED_MIGRATED);
-            virObjectEventStateQueue(driver->domainEventState, event);
-        }
 
         qemuMigrationParamsReset(driver, vm, QEMU_ASYNC_JOB_MIGRATION_OUT,
                                  priv->job.migParams, priv->job.apiFlags);
@@ -4624,11 +4620,7 @@ qemuMigrationSrcPerformJob(virQEMUDriverPtr driver,
         qemuMigrationParamsReset(driver, vm, QEMU_ASYNC_JOB_MIGRATION_OUT,
                                  priv->job.migParams, priv->job.apiFlags);
 
-    if (qemuMigrationSrcRestoreDomainState(driver, vm)) {
+    qemuMigrationSrcRestoreDomainState(driver, vm);
-        event = virDomainEventLifecycleNewFromObj(vm,
-                                         VIR_DOMAIN_EVENT_RESUMED,
-                                         VIR_DOMAIN_EVENT_RESUMED_MIGRATED);
-    }
 
     qemuMigrationJobFinish(driver, vm);
     if (!virDomainObjIsActive(vm) && ret == 0) {
@@ -4672,7 +4664,6 @@ qemuMigrationSrcPerformPhase(virQEMUDriverPtr driver,
                              unsigned long resource)
 {
     qemuDomainObjPrivatePtr priv = vm->privateData;
-    virObjectEventPtr event = NULL;
     int ret = -1;
 
     /* If we didn't start the job in the begin phase, start it now. */
@@ -4694,11 +4685,7 @@ qemuMigrationSrcPerformPhase(virQEMUDriverPtr driver,
                                         nmigrate_disks, migrate_disks, migParams);
 
     if (ret < 0) {
-        if (qemuMigrationSrcRestoreDomainState(driver, vm)) {
+        qemuMigrationSrcRestoreDomainState(driver, vm);
-            event = virDomainEventLifecycleNewFromObj(vm,
-                                                      VIR_DOMAIN_EVENT_RESUMED,
-                                                      VIR_DOMAIN_EVENT_RESUMED_MIGRATED);
-        }
         goto endjob;
     }
 
@@ -4722,7 +4709,6 @@ qemuMigrationSrcPerformPhase(virQEMUDriverPtr driver,
 
  cleanup:
     virDomainObjEndAPI(&vm);
-    virObjectEventStateQueue(driver->domainEventState, event);
     return ret;
 }
 
@@ -5074,13 +5060,8 @@ qemuMigrationDstFinish(virQEMUDriverPtr driver,
                 goto endjob;
         }
 
-        if (inPostCopy) {
+        if (inPostCopy)
             doKill = false;
-            event = virDomainEventLifecycleNewFromObj(vm,
-                                        VIR_DOMAIN_EVENT_RESUMED,
-                                        VIR_DOMAIN_EVENT_RESUMED_POSTCOPY);
-            virObjectEventStateQueue(driver->domainEventState, event);
-        }
     }
 
     if (mig->jobInfo) {
@@ -5111,10 +5092,20 @@ qemuMigrationDstFinish(virQEMUDriverPtr driver,
 
     dom = virGetDomain(dconn, vm->def->name, vm->def->uuid, vm->def->id);
 
-    event = virDomainEventLifecycleNewFromObj(vm,
+    if (inPostCopy) {
-                                              VIR_DOMAIN_EVENT_RESUMED,
+        /* The only RESUME event during post-copy migration is triggered by
-                                              VIR_DOMAIN_EVENT_RESUMED_MIGRATED);
+         * QEMU when the running domain moves from the source to the
-    virObjectEventStateQueue(driver->domainEventState, event);
+         * destination host, but then the migration keeps running until all
+         * modified memory is transferred from the source host. This will
+         * result in VIR_DOMAIN_EVENT_RESUMED with RESUMED_POSTCOPY detail.
+         * However, our API documentation says we need to fire another RESUMED
+         * event at the very end of migration with RESUMED_MIGRATED detail.
+         */
+        event = virDomainEventLifecycleNewFromObj(vm,
+                                                  VIR_DOMAIN_EVENT_RESUMED,
+                                                  VIR_DOMAIN_EVENT_RESUMED_MIGRATED);
+        virObjectEventStateQueue(driver->domainEventState, event);
+    }
 
     if (virDomainObjGetState(vm, NULL) == VIR_DOMAIN_PAUSED) {
         virDomainObjSetState(vm, VIR_DOMAIN_PAUSED, VIR_DOMAIN_PAUSED_USER);

src/qemu/qemu_process.c

@@ -456,7 +456,6 @@ qemuProcessFakeReboot(void *opaque)
     virDomainObjPtr vm = opaque;
     qemuDomainObjPrivatePtr priv = vm->privateData;
     virQEMUDriverPtr driver = priv->driver;
-    virObjectEventPtr event = NULL;
     virQEMUDriverConfigPtr cfg = virQEMUDriverGetConfig(driver);
     virDomainRunningReason reason = VIR_DOMAIN_RUNNING_BOOTED;
     int ret = -1, rc;
@@ -493,9 +492,6 @@ qemuProcessFakeReboot(void *opaque)
         goto endjob;
     }
     priv->gotShutdown = false;
-    event = virDomainEventLifecycleNewFromObj(vm,
-                                     VIR_DOMAIN_EVENT_RESUMED,
-                                     VIR_DOMAIN_EVENT_RESUMED_UNPAUSED);
 
     if (virDomainSaveStatus(driver->xmlopt, cfg->stateDir, vm, driver->caps) < 0) {
         VIR_WARN("Unable to save status on vm %s after state change",
@@ -511,7 +507,6 @@ qemuProcessFakeReboot(void *opaque)
     if (ret == -1)
         ignore_value(qemuProcessKill(vm, VIR_QEMU_PROCESS_KILL_FORCE));
     virDomainObjEndAPI(&vm);
-    virObjectEventStateQueue(driver->domainEventState, event);
     virObjectUnref(cfg);
 }
 
@@ -3109,7 +3104,10 @@ qemuProcessStartCPUs(virQEMUDriverPtr driver, virDomainObjPtr vm,
     if (ret < 0)
         goto release;
 
-    virDomainObjSetState(vm, VIR_DOMAIN_RUNNING, reason);
+    /* The RESUME event handler will change the domain state with the reason
+     * saved in priv->runningReason and it will also emit corresponding domain
+     * lifecycle event.
+     */
 
  cleanup:
     virObjectUnref(cfg);