runtime: sending SIGKILL to qemu

There is a race condition when virtiofsd is killed without finishing all
the clients. Because of that, when a pod is stopped, QEMU detects
virtiofsd is gone, which is legitimate.

Sending a SIGTERM first before killing could introduce some latency
during the shutdown.

Fixes kata-containers#6757.
Backport of kata-containers#6959.

Signed-off-by: Beraldo Leal <bleal@redhat.com>

src/runtime/virtcontainers/qemu.go

@@ -1108,22 +1108,21 @@ func (q *qemu) StopVM(ctx context.Context, waitOnly bool) (err error) {
 		return err
 	}
 
-	if waitOnly {
-		pids := q.GetPids()
-		if len(pids) == 0 {
-			return errors.New("cannot determine QEMU PID")
-		}
-
-		pid := pids[0]
+	pids := q.GetPids()
+	if len(pids) == 0 {
+		return errors.New("cannot determine QEMU PID")
+	}
+	pid := pids[0]
 
+	if waitOnly {
 		err := utils.WaitLocalProcess(pid, qemuStopSandboxTimeoutSecs, syscall.Signal(0), q.Logger())
 		if err != nil {
 			return err
 		}
 	} else {
-		err := q.qmpMonitorCh.qmp.ExecuteQuit(q.qmpMonitorCh.ctx)
+		err = syscall.Kill(pid, syscall.SIGKILL)
 		if err != nil {
-			q.Logger().WithError(err).Error("Fail to execute qmp QUIT")
+			q.Logger().WithError(err).Error("Fail to send SIGKILL to qemu")
 			return err
 		}
 	}