[Qemu-devel] [PATCH v5 7/7] RTC:Allow to migrate from old version

[Zhang, Yang Z]

The new logic is compatible with old. So should not block to migrate
from old version. But new version cannot migrate to old.

Signed-off-by: Yang Zhang <address@hidden>
---
 hw/mc146818rtc.c |   35 +++++++++++++++++++++++++++++++----
 1 files changed, 31 insertions(+), 4 deletions(-)

diff --git a/hw/mc146818rtc.c b/hw/mc146818rtc.c
index e6f221c..ec2a24c 100644
--- a/hw/mc146818rtc.c
+++ b/hw/mc146818rtc.c
@@ -846,11 +846,38 @@ static int rtc_post_load(void *opaque, int version_id)
     return 0;
 }

+static int rtc_load_old(QEMUFile *f, void *opaque, int version_id)
+{
+    RTCState *s = opaque;
+    uint8_t buf[77];
+
+    if (version_id > 2) {
+        return -EINVAL;
+    }
+
+    qemu_get_buffer(f, s->cmos_data, sizeof(s->cmos_data));
+    /* dummy load for compatibility */
+    qemu_get_buffer(f, buf, 77);
+
+    rtc_set_time(s);
+    rtc_set_offset(s, 0);
+    periodic_timer_update(s,  qemu_get_clock_ns(rtc_clock));
+    check_update_timer(s);
+
+#ifdef TARGET_I386
+    if (s->lost_tick_policy == LOST_TICK_SLEW) {
+        rtc_coalesced_timer_update(s);
+    }
+#endif
+    return 0;
+}
+
 static const VMStateDescription vmstate_rtc = {
     .name = "mc146818rtc",
-    .version_id = 2,
-    .minimum_version_id = 1,
-    .minimum_version_id_old = 1,
+    .version_id = 3,
+    .minimum_version_id = 3,
+    .minimum_version_id_old = 2,
+    .load_state_old = rtc_load_old,
     .post_load = rtc_post_load,
     .fields      = (VMStateField []) {
         VMSTATE_BUFFER(cmos_data, RTCState),
@@ -988,7 +1015,7 @@ static int rtc_initfn(ISADevice *dev)
     memory_region_init_io(&s->io, &cmos_ops, s, "rtc", 2);
     isa_register_ioport(dev, &s->io, base);

-    qdev_set_legacy_instance_id(&dev->qdev, base, 2);
+    qdev_set_legacy_instance_id(&dev->qdev, base, 3);
     qemu_register_reset(rtc_reset, s);

     object_property_add(OBJECT(s), "date", "struct tm",
--
1.7.1