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From 91a37e3641afbd29067cd945ca14a6572e4d4897 Mon Sep 17 00:00:00 2001
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Message-Id: <91a37e3641afbd29067cd945ca14a6572e4d4897@dist-git>
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From: Jiri Denemark <jdenemar@redhat.com>
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Date: Thu, 15 Nov 2018 11:16:43 +0100
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Subject: [PATCH] qemu: Fix post-copy migration on the source
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Post-copy migration has been broken on the source since commit
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v3.8.0-245-g32c29f10db which implemented support for
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pause-before-switchover QEMU migration capability.
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Even though the migration itself went well, the source did not really
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know when it switched to the post-copy mode despite the messages logged
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by MIGRATION event handler. As a result of this, the events emitted by
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source libvirtd were not accurate and statistics of the completed
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migration would cover only the pre-copy part of migration. Moreover, if
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migration failed during the post-copy phase for some reason, the source
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libvirtd would just happily resume the domain, which could lead to disk
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corruption.
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With the pause-before-switchover capability enabled, the order of events
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emitted by QEMU changed:
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                    pause-before-switchover
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           disabled                        enabled
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    MIGRATION, postcopy-active      STOP
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    STOP                            MIGRATION, pre-switchover
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                                    MIGRATION, postcopy-active
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The STOP even handler checks the migration status (postcopy-active) and
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sets the domain state accordingly. Which is sufficient when
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pause-before-switchover is disabled, but once we enable it, the
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migration status is still active when we get STOP from QEMU. Thus the
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domain state set in the STOP handler has to be corrected once we are
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notified that migration changed to postcopy-active.
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This results in two SUSPENDED events to be emitted by the source
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libvirtd during post-copy migration. The first one with
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VIR_DOMAIN_EVENT_SUSPENDED_MIGRATED detail, while the second one reports
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the corrected VIR_DOMAIN_EVENT_SUSPENDED_POSTCOPY detail. This is
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inevitable because we don't know whether migration will eventually
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switch to post-copy at the time we emit the first event.
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https://bugzilla.redhat.com/show_bug.cgi?id=1647365
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Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
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Reviewed-by: Ján Tomko <jtomko@redhat.com>
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(cherry picked from commit eca9d21e6cc8129ec4426fbf1ace30e215b9cfbc)
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https://bugzilla.redhat.com/show_bug.cgi?id=1649169
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https://bugzilla.redhat.com/show_bug.cgi?id=1654732
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Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
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---
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 src/qemu/qemu_process.c | 26 +++++++++++++++++++++++++-
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 1 file changed, 25 insertions(+), 1 deletion(-)
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diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c
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index 4b99fbd835..2d2954ba18 100644
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--- a/src/qemu/qemu_process.c
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+++ b/src/qemu/qemu_process.c
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@@ -1522,9 +1522,13 @@ static int
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 qemuProcessHandleMigrationStatus(qemuMonitorPtr mon ATTRIBUTE_UNUSED,
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                                  virDomainObjPtr vm,
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                                  int status,
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-                                 void *opaque ATTRIBUTE_UNUSED)
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+                                 void *opaque)
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 {
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     qemuDomainObjPrivatePtr priv;
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+    virQEMUDriverPtr driver = opaque;
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+    virObjectEventPtr event = NULL;
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+    virQEMUDriverConfigPtr cfg = virQEMUDriverGetConfig(driver);
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+    int reason;
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     virObjectLock(vm);
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@@ -1541,8 +1545,28 @@ qemuProcessHandleMigrationStatus(qemuMonitorPtr mon ATTRIBUTE_UNUSED,
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     priv->job.current->stats.mig.status = status;
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     virDomainObjBroadcast(vm);
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+    if (status == QEMU_MONITOR_MIGRATION_STATUS_POSTCOPY &&
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+        virDomainObjGetState(vm, &reason) == VIR_DOMAIN_PAUSED &&
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+        reason == VIR_DOMAIN_PAUSED_MIGRATION) {
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+        VIR_DEBUG("Correcting paused state reason for domain %s to %s",
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+                  vm->def->name,
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+                  virDomainPausedReasonTypeToString(VIR_DOMAIN_PAUSED_POSTCOPY));
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+
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+        virDomainObjSetState(vm, VIR_DOMAIN_PAUSED, VIR_DOMAIN_PAUSED_POSTCOPY);
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+        event = virDomainEventLifecycleNewFromObj(vm,
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+                                                  VIR_DOMAIN_EVENT_SUSPENDED,
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+                                                  VIR_DOMAIN_EVENT_SUSPENDED_POSTCOPY);
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+
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+        if (virDomainSaveStatus(driver->xmlopt, cfg->stateDir, vm, driver->caps) < 0) {
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+            VIR_WARN("Unable to save status on vm %s after state change",
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+                     vm->def->name);
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+        }
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+    }
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+
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  cleanup:
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     virObjectUnlock(vm);
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+    virObjectEventStateQueue(driver->domainEventState, event);
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+    virObjectUnref(cfg);
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     return 0;
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 }
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-- 
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2.19.2
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