target-s390x: implement STPT helper

Save the timer target value in the SPT helper, so that the STPT helper
can compute the remaining time.

This allow the Linux kernel to correctly do time accounting.
Signed-off-by: NAurelien Jarno <aurelien@aurel32.net>
Signed-off-by: NAlexander Graf <agraf@suse.de>

target-s390x/misc_helper.c

@@ -313,14 +313,15 @@ void HELPER(spt)(CPUS390XState *env, uint64_t time)
     /* nanoseconds */
     time = tod2time(time);
 
-    timer_mod(env->cpu_timer, qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) + time);
+    env->cputm = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) + time;
+
+    timer_mod(env->cpu_timer, env->cputm);
 }
 
 /* Store CPU Timer */
 uint64_t HELPER(stpt)(CPUS390XState *env)
 {
-    /* XXX implement */
-    return 0;
+    return time2tod(env->cputm - qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL));
 }
 
 /* Store System Information */