s390x/tcg: SET CLOCK COMPARATOR can clear CKC interrupts

Let's stop the timer and delete any pending CKC IRQ before doing
anything else.

While at it, add a comment why the check for ckc == -1ULL is needed.

Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
Message-Id: <20180627134410.4901-7-david@redhat.com>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/target/s390x/misc_helper.c b/target/s390x/misc_helper.c
index 229f14d3da..e4c1522140 100644
--- a/target/s390x/misc_helper.c
+++ b/target/s390x/misc_helper.c
@@ -154,6 +154,13 @@ void HELPER(sckc)(CPUS390XState *env, uint64_t time)
 {
     S390TODState *td = s390_get_todstate();
 
+    /* stop the timer and remove pending CKC IRQs */
+    timer_del(env->tod_timer);
+    qemu_mutex_lock_iothread();
+    env->pending_int &= ~INTERRUPT_EXT_CLOCK_COMPARATOR;
+    qemu_mutex_unlock_iothread();
+
+    /* the tod has to exceed the ckc, this can never happen if ckc is all 1's */
     if (time == -1ULL) {
         return;
     }