Re: [libvirt] [PATCH] qemu: Fix post-copy migration on the source

Post-copy migration has been broken on the source since commit v3.8.0-245-g32c29f10db which implemented support for pause-before-switchover QEMU migration capability. Even though the migration itself went well, the source did not really know when it switched to the post-copy mode despite the messages logged by MIGRATION event handler. As a result of this, the events emitted by source libvirtd were not accurate and statistics of the completed migration would cover only the pre-copy part of migration. Moreover, if migration failed during the post-copy phase for some reason, the source libvirtd would just happily resume the domain, which could lead to disk corruption. With the pause-before-switchover capability enabled, the order of events emitted by QEMU changed: pause-before-switchover disabled enabled MIGRATION, potcopy-active STOP

STOP MIGRATION, pre-switchover MIGRATION, postcopy-active The STOP even handler checks the migration status (postcopy-active) and sets the domain state accordingly. Which is sufficient when pause-before-switchover is disabled, but once we enable it, the migration status is still active when we get STOP from QEMU. Thus the domain state set in the STOP handler has to be corrected once we are notified that migration changed to postcopy-active. This results in two SUSPENDED events to be emitted by the source libvirtd during post-copy migration. The first one with VIR_DOMAIN_EVENT_SUSPENDED_MIGRATED detail, while the second one reports the corrected VIR_DOMAIN_EVENT_SUSPENDED_POSTCOPY detail. This is inevitable because we don't know whether migration will eventually switch to post-copy at the time we emit the first event. https://bugzilla.redhat.com/show_bug.cgi?id=1647365 Signed-off-by: Jiri Denemark <jdenemar(a)redhat.com&gt; --- src/qemu/qemu_process.c | 26 +++++++++++++++++++++++++- 1 file changed, 25 insertions(+), 1 deletion(-)