s390x/tcg: handle WAIT PSWs during interrupt injection

If we encounter a WAIT PSW, we have to halt immediately. Using
cpu_loop_exit() at this point feels wrong. Simply leaving
cs->exception_index set doesn't result in an immediate stop.

This is also necessary to properly handle SIGP STOP interrupts later.

The CPU_INTERRUPT_HALT will be processed immediately and properly set
the CPU to halted (also resetting cs->exception_index to EXCP_HLT)
Signed-off-by: NDavid Hildenbrand <david@redhat.com>
Message-Id: <20170928203708.9376-10-david@redhat.com>
Reviewed-by: NRichard Henderson <richard.henderson@linaro.org>
Signed-off-by: NCornelia Huck <cohuck@redhat.com>

target/s390x/excp_helper.c

@@ -468,6 +468,12 @@ void s390_cpu_do_interrupt(CPUState *cs)
         do_mchk_interrupt(env);
         break;
     }
+
+    /* WAIT PSW during interrupt injection */
+    if (cs->exception_index == EXCP_HLT) {
+        /* don't trigger a cpu_loop_exit(), use an interrupt instead */
+        cpu_interrupt(CPU(cpu), CPU_INTERRUPT_HALT);
+    }
     cs->exception_index = -1;
 
     /* we might still have pending interrupts, but not deliverable */