[Qemu-devel] [PATCHv3 8/9] pseries: Move rtc_offset into RTC device's state structure

[David Gibson <david@gibson.dropbear.id.au>]

The initial creation of the PAPR RTC qdev class left a wart - the rtc's
offset was left in the sPAPREnvironment structure, accessed via a global.

This patch moves it into the RTC device's own state structure, were it
belongs.  This requires a small change to the migration stream format.  In
order to handle incoming streams from older versions, we also need to
retain the rtc_offset field in the sPAPREnvironment structure, so that it
can be loaded into via the vmsd, then pushed into the RTC device.

Since we're changing the migration format, this also takes the opportunity
to:

  * Change the rtc offset from a value in seconds to a value in
    nanoseconds, allowing nanosecond offsets between host and guest
    rtc time, if desired.

  * Remove both the already unused "next_irq" field and now unused
    "rtc_offset" field from the new version of the spapr migration
    stream

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
 hw/ppc/spapr.c         | 30 +++++++++++++++++++++++++++---
 hw/ppc/spapr_rtc.c     | 41 +++++++++++++++++++++++++++++++++++++----
 include/hw/ppc/spapr.h |  3 ++-
 3 files changed, 66 insertions(+), 8 deletions(-)

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index 688adae..2264802 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -1018,15 +1018,39 @@ static int spapr_vga_init(PCIBus *pci_bus)
     }
 }
 
+static int spapr_post_load(void *opaque, int version_id)
+{
+    sPAPREnvironment *spapr = (sPAPREnvironment *)opaque;
+    int err = 0;
+
+    /* In earlier versions, there was no seperate qdev for the PAPR
+     * RTC, so the RTC offset was stored directly in sPAPREnvironment.
+     * So when migrating from those versions, poke the incoming offset
+     * value into the RTC device */
+    if (version_id < 3) {
+        err = spapr_rtc_import_offset(spapr->rtc, spapr->rtc_offset);
+    }
+
+    return err;
+}
+
+static bool version_before_3(void *opaque, int version_id)
+{
+    return version_id < 3;
+}
+
 static const VMStateDescription vmstate_spapr = {
     .name = "spapr",
-    .version_id = 2,
+    .version_id = 3,
     .minimum_version_id = 1,
+    .post_load = spapr_post_load,
     .fields = (VMStateField[]) {
-        VMSTATE_UNUSED(4), /* used to be @next_irq */
+        /* used to be @next_irq */
+        VMSTATE_UNUSED_BUFFER(version_before_3, 0, 4),
 
         /* RTC offset */
-        VMSTATE_UINT64(rtc_offset, sPAPREnvironment),
+        VMSTATE_UINT64_TEST(rtc_offset, sPAPREnvironment, version_before_3),
+
         VMSTATE_PPC_TIMEBASE_V(tb, sPAPREnvironment, 2),
         VMSTATE_END_OF_LIST()
     },
diff --git a/hw/ppc/spapr_rtc.c b/hw/ppc/spapr_rtc.c
index b9f4704..5ad0823 100644
--- a/hw/ppc/spapr_rtc.c
+++ b/hw/ppc/spapr_rtc.c
@@ -37,6 +37,7 @@ typedef struct sPAPRRTCState sPAPRRTCState;
 struct sPAPRRTCState {
     /*< private >*/
     SysBusDevice parent_obj;
+    int64_t ns_offset;
 };
 
 #define NSEC_PER_SEC    1000000000LL
@@ -45,20 +46,37 @@ void spapr_rtc_read(DeviceState *dev, struct tm *tm, uint32_t *ns)
 {
     sPAPRRTCState *rtc = SPAPR_RTC(dev);
     int64_t host_ns = qemu_clock_get_ns(rtc_clock);
+    int64_t guest_ns;
     time_t guest_s;
 
     assert(rtc);
 
-    guest_s = host_ns / NSEC_PER_SEC + spapr->rtc_offset;
+    guest_ns = host_ns + rtc->ns_offset;
+    guest_s = guest_ns / NSEC_PER_SEC;
 
     if (tm) {
         gmtime_r(&guest_s, tm);
     }
     if (ns) {
-        *ns = host_ns % NSEC_PER_SEC;
+        *ns = guest_ns;
     }
 }
 
+int spapr_rtc_import_offset(DeviceState *dev, int64_t legacy_offset)
+{
+    sPAPRRTCState *rtc;
+
+    if (!dev) {
+        return -ENODEV;
+    }
+
+    rtc = SPAPR_RTC(dev);
+
+    rtc->ns_offset = legacy_offset * NSEC_PER_SEC;
+
+    return 0;
+}
+
 static void rtas_get_time_of_day(PowerPCCPU *cpu, sPAPREnvironment *spapr,
                                  uint32_t token, uint32_t nargs,
                                  target_ulong args,
@@ -94,6 +112,7 @@ static void rtas_set_time_of_day(PowerPCCPU *cpu, sPAPREnvironment *spapr,
                                  target_ulong args,
                                  uint32_t nret, target_ulong rets)
 {
+    sPAPRRTCState *rtc;
     struct tm tm;
     time_t new_s;
     int64_t host_ns;
@@ -124,15 +143,18 @@ static void rtas_set_time_of_day(PowerPCCPU *cpu, sPAPREnvironment *spapr,
     /* Generate a monitor event for the change */
     qapi_event_send_rtc_change(qemu_timedate_diff(&tm), &error_abort);
 
+    rtc = SPAPR_RTC(spapr->rtc);
+
     host_ns = qemu_clock_get_ns(rtc_clock);
 
-    spapr->rtc_offset = new_s - host_ns / NSEC_PER_SEC;
+    rtc->ns_offset = (new_s * NSEC_PER_SEC) - host_ns;
 
     rtas_st(rets, 0, RTAS_OUT_SUCCESS);
 }
 
 static void spapr_rtc_realize(DeviceState *dev, Error **errp)
 {
+    sPAPRRTCState *rtc = SPAPR_RTC(dev);
     struct tm tm;
     time_t host_s;
     int64_t rtc_ns;
@@ -142,14 +164,25 @@ static void spapr_rtc_realize(DeviceState *dev, Error **errp)
     qemu_get_timedate(&tm, 0);
     host_s = mktimegm(&tm);
     rtc_ns = qemu_clock_get_ns(rtc_clock);
-    spapr->rtc_offset = host_s - rtc_ns / NSEC_PER_SEC;
+    rtc->ns_offset = host_s * NSEC_PER_SEC - rtc_ns;
 }
 
+static const VMStateDescription vmstate_spapr_rtc = {
+    .name = "spapr/rtc",
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .fields = (VMStateField[]) {
+        VMSTATE_INT64(ns_offset, sPAPRRTCState),
+        VMSTATE_END_OF_LIST()
+    },
+};
+
 static void spapr_rtc_class_init(ObjectClass *oc, void *data)
 {
     DeviceClass *dc = DEVICE_CLASS(oc);
 
     dc->realize = spapr_rtc_realize;
+    dc->vmsd = &vmstate_spapr_rtc;
 
     spapr_rtas_register(RTAS_GET_TIME_OF_DAY, "get-time-of-day",
                         rtas_get_time_of_day);
diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
index 9a7bf36..6a4f982 100644
--- a/include/hw/ppc/spapr.h
+++ b/include/hw/ppc/spapr.h
@@ -27,7 +27,7 @@ typedef struct sPAPREnvironment {
     void *rtas_blob;
     void *fdt_skel;
     target_ulong entry_point;
-    uint64_t rtc_offset;
+    uint64_t rtc_offset; /* Now used only during incoming migration */
     struct PPCTimebase tb;
     bool has_graphics;
 
@@ -485,5 +485,6 @@ int spapr_tcet_dma_dt(void *fdt, int node_off, const char *propname,
 #define TYPE_SPAPR_RTC "spapr-rtc"
 
 void spapr_rtc_read(DeviceState *dev, struct tm *tm, uint32_t *ns);
+int spapr_rtc_import_offset(DeviceState *dev, int64_t legacy_offset);
 
 #endif /* !defined (__HW_SPAPR_H__) */
-- 
2.1.0