s390x: load_psw() should only exchange the PSW for KVM

Let's simplify it a bit. On some weird circumstances we would have
tried to recompute watchpoints when running under KVM. load_psw() is
called from do_restart_interrupt() during a SIGP RESTART if the target
CPU is STOPPED. Let's touch watchpoints only in the TCG case - where
they are used for PER emulation.
Signed-off-by: NDavid Hildenbrand <david@redhat.com>
Message-Id: <20180409113019.14568-3-david@redhat.com>
Acked-by: NChristian Borntraeger <borntraeger@de.ibm.com>
Reviewed-by: NThomas Huth <thuth@redhat.com>
Signed-off-by: NCornelia Huck <cohuck@redhat.com>

target/s390x/helper.c

@@ -103,16 +103,18 @@ void load_psw(CPUS390XState *env, uint64_t mask, uint64_t addr)
 
     env->psw.addr = addr;
     env->psw.mask = mask;
-    if (tcg_enabled()) {
-        env->cc_op = (mask >> 44) & 3;
+
+    /* KVM will handle all WAITs and trigger a WAIT exit on disabled_wait */
+    if (!tcg_enabled()) {
+        return;
     }
+    env->cc_op = (mask >> 44) & 3;
 
     if ((old_mask ^ mask) & PSW_MASK_PER) {
         s390_cpu_recompute_watchpoints(CPU(s390_env_get_cpu(env)));
     }
 
-    /* KVM will handle all WAITs and trigger a WAIT exit on disabled_wait */
-    if (tcg_enabled() && (mask & PSW_MASK_WAIT)) {
+    if (mask & PSW_MASK_WAIT) {
         s390_handle_wait(s390_env_get_cpu(env));
     }
 }