s390x/tcg: STOPPED cpus can never wake up

Interrupts can't wake such CPUs up. SIGP from other CPUs has to be used
to toggle the state.
Reviewed-by: NRichard Henderson <richard.henderson@linaro.org>
Signed-off-by: NDavid Hildenbrand <david@redhat.com>
Message-Id: <20170928203708.9376-7-david@redhat.com>
Signed-off-by: NCornelia Huck <cohuck@redhat.com>

target/s390x/cpu.c

@@ -57,6 +57,12 @@ static bool s390_cpu_has_work(CPUState *cs)
 {
     S390CPU *cpu = S390_CPU(cs);
 
+    /* STOPPED cpus can never wake up */
+    if (s390_cpu_get_state(cpu) != CPU_STATE_LOAD &&
+        s390_cpu_get_state(cpu) != CPU_STATE_OPERATING) {
+        return false;
+    }
+
     if (!(cs->interrupt_request & CPU_INTERRUPT_HARD)) {
         return false;
     }