1 files changed, 26 insertions, 12 deletions

diff --git a/hw/pl031.c b/hw/pl031.c
index 713f85d836..9602664da6 100644
--- a/hw/pl031.c
+++ b/hw/pl031.c
@@ -13,6 +13,7 @@
 
 #include "sysbus.h"
 #include "qemu-timer.h"
+#include "sysemu.h"
 
 //#define DEBUG_PL031
 
@@ -38,6 +39,11 @@ typedef struct {
     QEMUTimer *timer;
     qemu_irq irq;
 
+    /* Needed to preserve the tick_count across migration, even if the
+     * absolute value of the rtc_clock is different on the source and
+     * destination.
+     */
+    uint32_t tick_offset_vmstate;
     uint32_t tick_offset;
 
     uint32_t mr;
@@ -68,27 +74,23 @@ static void pl031_interrupt(void * opaque)
 
 static uint32_t pl031_get_count(pl031_state *s)
 {
-    /* This assumes qemu_get_clock_ns returns the time since the machine was
-       created.  */
-    return s->tick_offset + qemu_get_clock_ns(vm_clock) / get_ticks_per_sec();
+    int64_t now = qemu_get_clock_ns(rtc_clock);
+    return s->tick_offset + now / get_ticks_per_sec();
 }
 
 static void pl031_set_alarm(pl031_state *s)
 {
-    int64_t now;
     uint32_t ticks;
 
-    now = qemu_get_clock_ns(vm_clock);
-    ticks = s->tick_offset + now / get_ticks_per_sec();
-
     /* The timer wraps around.  This subtraction also wraps in the same way,
        and gives correct results when alarm < now_ticks.  */
-    ticks = s->mr - ticks;
+    ticks = s->mr - pl031_get_count(s);
     DPRINTF("Alarm set in %ud ticks\n", ticks);
     if (ticks == 0) {
         qemu_del_timer(s->timer);
         pl031_interrupt(s);
     } else {
+        int64_t now = qemu_get_clock_ns(rtc_clock);
         qemu_mod_timer(s->timer, now + (int64_t)ticks * get_ticks_per_sec());
     }
 }
@@ -190,18 +192,29 @@ static int pl031_init(SysBusDevice *dev)
     sysbus_init_mmio(dev, &s->iomem);
 
     sysbus_init_irq(dev, &s->irq);
-    /* ??? We assume vm_clock is zero at this point.  */
     qemu_get_timedate(&tm, 0);
-    s->tick_offset = mktimegm(&tm);
+    s->tick_offset = mktimegm(&tm) - qemu_get_clock_ns(rtc_clock) / get_ticks_per_sec();
 
-    s->timer = qemu_new_timer_ns(vm_clock, pl031_interrupt, s);
+    s->timer = qemu_new_timer_ns(rtc_clock, pl031_interrupt, s);
     return 0;
 }
 
+static void pl031_pre_save(void *opaque)
+{
+    pl031_state *s = opaque;
+
+    /* tick_offset is base_time - rtc_clock base time.  Instead, we want to
+     * store the base time relative to the vm_clock for backwards-compatibility.  */
+    int64_t delta = qemu_get_clock_ns(rtc_clock) - qemu_get_clock_ns(vm_clock);
+    s->tick_offset_vmstate = s->tick_offset + delta / get_ticks_per_sec();
+}
+
 static int pl031_post_load(void *opaque, int version_id)
 {
     pl031_state *s = opaque;
 
+    int64_t delta = qemu_get_clock_ns(rtc_clock) - qemu_get_clock_ns(vm_clock);
+    s->tick_offset = s->tick_offset_vmstate - delta / get_ticks_per_sec();
     pl031_set_alarm(s);
     return 0;
 }
@@ -210,9 +223,10 @@ static const VMStateDescription vmstate_pl031 = {
     .name = "pl031",
     .version_id = 1,
     .minimum_version_id = 1,
+    .pre_save = pl031_pre_save,
     .post_load = pl031_post_load,
     .fields = (VMStateField[]) {
-        VMSTATE_UINT32(tick_offset, pl031_state),
+        VMSTATE_UINT32(tick_offset_vmstate, pl031_state),
         VMSTATE_UINT32(mr, pl031_state),
         VMSTATE_UINT32(lr, pl031_state),
         VMSTATE_UINT32(cr, pl031_state),