[pve-devel] [PATCH qemu-server 2/2] migrate: resume initially running VM when failing after convergence

[Fabian Ebner]

When phase2() is aborted after the migration already converged, then
after migrate_cancel, the VM might be in POSTMIGRATE state.

(There also is a conditional for SHUTDOWN state in QEMU's
migration_iteration_finish(), so it's likely possible to end up there
if the VM is shut down at the right time during migration, but no need
to resume then).

Detect the POSTMIGRATE state and resume the VM if it wasn't paused at
the beginning of the migration. There is no direct way to go to
PAUSED, so just print an error if the VM was paused at the beginning
of the migration.

Reported-by: Fabian Grünbichler <f.gruenbichler at proxmox.com>
Signed-off-by: Fabian Ebner <f.ebner at proxmox.com>
---
 PVE/QemuMigrate.pm | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/PVE/QemuMigrate.pm b/PVE/QemuMigrate.pm
index c293e294..dfe92325 100644
--- a/PVE/QemuMigrate.pm
+++ b/PVE/QemuMigrate.pm
@@ -1056,6 +1056,22 @@ sub phase2_cleanup {
     };
     $self->log('info', "migrate_cancel error: $@") if $@;
 
+    my $vm_status = eval {
+	mon_cmd($vmid, 'query-status')->{status} or die "no 'status' in result\n";
+    };
+    $self->log('err', "query-status error: $@") if $@;
+
+    # Can end up in POSTMIGRATE state if failure occurred after convergence. Try going back to
+    # original state. Unfortunately, direct transition from POSTMIGRATE to PAUSED is not possible.
+    if ($vm_status && $vm_status eq 'postmigrate') {
+	if (!$self->{vm_was_paused}) {
+	    eval { mon_cmd($vmid, 'cont'); };
+	    $self->log('err', "resuming VM failed: $@") if $@;
+	} else {
+	    $self->log('err', "VM was paused, but ended in postmigrate state");
+	}
+    }
+
     my $conf = $self->{vmconf};
     delete $conf->{lock};
     eval { PVE::QemuConfig->write_config($vmid, $conf) };
-- 
2.30.2