cpu-exec: simplify init_delay_params

With the introduction of QEMU_CLOCK_VIRTUAL_RT, the computation of
sc->diff_clk can be simplified nicely:

        qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) -
        qemu_clock_get_ns(QEMU_CLOCK_REALTIME) +
        cpu_get_clock_offset()

     =  qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) -
        (qemu_clock_get_ns(QEMU_CLOCK_REALTIME) - cpu_get_clock_offset())

     =  qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) -
        (qemu_clock_get_ns(QEMU_CLOCK_REALTIME) + timers_state.cpu_clock_offset)

     =  qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) -
        qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL_RT)

Cc: Sebastian Tanase <sebastian.tanase@openwide.fr>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

cpu-exec.c

@@ -100,10 +100,8 @@ static void init_delay_params(SyncClocks *sc,
     if (!icount_align_option) {
         return;
     }
-    sc->realtime_clock = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
-    sc->diff_clk = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) -
-                   sc->realtime_clock +
-                   cpu_get_clock_offset();
+    sc->realtime_clock = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL_RT);
+    sc->diff_clk = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) - sc->realtime_clock;
     sc->last_cpu_icount = cpu->icount_extra + cpu->icount_decr.u16.low;
     if (sc->diff_clk < max_delay) {
         max_delay = sc->diff_clk;

cpus.c

@@ -229,23 +229,6 @@ int64_t cpu_get_clock(void)
     return ti;
 }
 
-/* return the offset between the host clock and virtual CPU clock */
-int64_t cpu_get_clock_offset(void)
-{
-    int64_t ti;
-    unsigned start;
-
-    do {
-        start = seqlock_read_begin(&timers_state.vm_clock_seqlock);
-        ti = timers_state.cpu_clock_offset;
-        if (!timers_state.cpu_ticks_enabled) {
-            ti -= get_clock();
-        }
-    } while (seqlock_read_retry(&timers_state.vm_clock_seqlock, start));
-
-    return -ti;
-}
-
 /* enable cpu_get_ticks()
  * Caller must hold BQL which server as mutex for vm_clock_seqlock.
  */

include/qemu/timer.h

@@ -838,7 +838,6 @@ static inline int64_t get_clock(void)
 int64_t cpu_get_icount_raw(void);
 int64_t cpu_get_icount(void);
 int64_t cpu_get_clock(void);
-int64_t cpu_get_clock_offset(void);
 int64_t cpu_icount_to_ns(int64_t icount);
 
 /*******************************************/