qemu: Report the offset from host UTC for RTC_CHANGE event

https://bugzilla.redhat.com/show_bug.cgi?id=964177

Though both libvirt and QEMU's document say RTC_CHANGE returns
the offset from the host UTC, qemu actually returns the offset
from the specified date instead when specific date is provided
(-rtc base=$date).

It's not safe for qemu to fix it in code, it worked like that
for 3 years, changing it now may break other QEMU use cases.
What qemu tries to do is to fix the document:

http://lists.gnu.org/archive/html/qemu-devel/2013-05/msg04782.html

And in libvirt side, instead of replying on the value from qemu,
this converts the offset returned from qemu to the offset from
host UTC, by:

  /*
   * a: the offset from qemu RTC_CHANGE event
   * b: The specified date (-rtc base=$date)
   * c: the host date when libvirt gets the RTC_CHANGE event
   * offset: What libvirt will report
   */

  offset = a + (b - c);

The specified date (-rtc base=$date) is recorded in clock's def as
an internal only member (may be useful to exposed outside?).

Internal only XML tag "basetime" is introduced to not lose the
guest's basetime after libvirt restarting/reloading:

<clock offset='variable' adjustment='304' basis='utc' basetime='1370423588'/>

diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
index 80deac47874b402858400228cf2c9ff96da8a5e5..3e810139159d5ba6e4eb41ecb2faa65b658abb5c 100644 (file)
--- a/src/conf/domain_conf.c
+++ b/src/conf/domain_conf.c
@@ -96,6 +96,7 @@ typedef enum {
    VIR_DOMAIN_XML_INTERNAL_PCI_ORIG_STATES = (1<<18),
    VIR_DOMAIN_XML_INTERNAL_ALLOW_ROM = (1<<19),
    VIR_DOMAIN_XML_INTERNAL_ALLOW_BOOT = (1<<20),
+   VIR_DOMAIN_XML_INTERNAL_BASEDATE = (1 << 21),
 } virDomainXMLInternalFlags;
 
 VIR_ENUM_IMPL(virDomainTaint, VIR_DOMAIN_TAINT_LAST,
@@ -11193,6 +11194,16 @@ virDomainDefParseXML(xmlDocPtr xml,
         break;
     }
 
+    if (def->clock.offset == VIR_DOMAIN_CLOCK_OFFSET_VARIABLE &&
+        flags & VIR_DOMAIN_XML_INTERNAL_BASEDATE) {
+        if (virXPathULongLong("number(./clock/@basedate)", ctxt,
+                              &def->clock.data.variable.basedate) < 0) {
+            virReportError(VIR_ERR_XML_ERROR, "%s",
+                           _("invalid basedate"));
+            goto error;
+        }
+    }
+
     if ((n = virXPathNodeSet("./clock/timer", ctxt, &nodes)) < 0)
         goto error;
 
@@ -15788,7 +15799,8 @@ virDomainResourceDefFormat(virBufferPtr buf,
 
 verify(((VIR_DOMAIN_XML_INTERNAL_STATUS |
          VIR_DOMAIN_XML_INTERNAL_ACTUAL_NET |
-         VIR_DOMAIN_XML_INTERNAL_PCI_ORIG_STATES)
+         VIR_DOMAIN_XML_INTERNAL_PCI_ORIG_STATES |
+         VIR_DOMAIN_XML_INTERNAL_BASEDATE)
         & DUMPXML_FLAGS) == 0);
 
 /* This internal version can accept VIR_DOMAIN_XML_INTERNAL_*,
@@ -15810,7 +15822,8 @@ virDomainDefFormatInternal(virDomainDefPtr def,
     virCheckFlags(DUMPXML_FLAGS |
                   VIR_DOMAIN_XML_INTERNAL_STATUS |
                   VIR_DOMAIN_XML_INTERNAL_ACTUAL_NET |
-                  VIR_DOMAIN_XML_INTERNAL_PCI_ORIG_STATES,
+                  VIR_DOMAIN_XML_INTERNAL_PCI_ORIG_STATES |
+                  VIR_DOMAIN_XML_INTERNAL_BASEDATE,
                   -1);
 
     if (!(type = virDomainVirtTypeToString(def->virtType))) {
@@ -16208,6 +16221,10 @@ virDomainDefFormatInternal(virDomainDefPtr def,
         virBufferAsprintf(buf, " adjustment='%lld' basis='%s'",
                           def->clock.data.variable.adjustment,
                           virDomainClockBasisTypeToString(def->clock.data.variable.basis));
+
+        if (flags & VIR_DOMAIN_XML_INTERNAL_BASEDATE)
+            virBufferAsprintf(buf, " basedate='%llu'",
+                              def->clock.data.variable.basedate);
         break;
     case VIR_DOMAIN_CLOCK_OFFSET_TIMEZONE:
         virBufferEscapeString(buf, " timezone='%s'", def->clock.data.timezone);
@@ -16586,7 +16603,8 @@ virDomainSaveStatus(virDomainXMLOptionPtr xmlopt,
     unsigned int flags = (VIR_DOMAIN_XML_SECURE |
                           VIR_DOMAIN_XML_INTERNAL_STATUS |
                           VIR_DOMAIN_XML_INTERNAL_ACTUAL_NET |
-                          VIR_DOMAIN_XML_INTERNAL_PCI_ORIG_STATES);
+                          VIR_DOMAIN_XML_INTERNAL_PCI_ORIG_STATES |
+                          VIR_DOMAIN_XML_INTERNAL_BASEDATE);
 
     int ret = -1;
     char *xml;
@@ -16674,7 +16692,8 @@ virDomainObjListLoadStatus(virDomainObjListPtr doms,
     if (!(obj = virDomainObjParseFile(statusFile, caps, xmlopt, expectedVirtTypes,
                                       VIR_DOMAIN_XML_INTERNAL_STATUS |
                                       VIR_DOMAIN_XML_INTERNAL_ACTUAL_NET |
-                                      VIR_DOMAIN_XML_INTERNAL_PCI_ORIG_STATES)))
+                                      VIR_DOMAIN_XML_INTERNAL_PCI_ORIG_STATES |
+                                      VIR_DOMAIN_XML_INTERNAL_BASEDATE)))
         goto error;
 
     virUUIDFormat(obj->def->uuid, uuidstr);

diff --git a/src/conf/domain_conf.h b/src/conf/domain_conf.h
index 3a71d6c8f57b9c019ba76c6fc35c18f76c22960e..b8edb1e80ccfc5624e053b845085e048dedef045 100644 (file)
--- a/src/conf/domain_conf.h
+++ b/src/conf/domain_conf.h
@@ -1767,6 +1767,11 @@ struct _virDomainClockDef {
         struct {
             long long adjustment;
             int basis;
+
+            /* Store the base date (-rtc base=$date, in seconds
+             * since the Epoch) of guest process, internal only
+             */
+            unsigned long long basedate;
         } variable;
 
         /* Timezone name, when

diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
index 71be3ff0d521ecbbbf5abbcd360a1e33e4889571..486682e77c068389eb9a495920a05802d7ab94c0 100644 (file)
--- a/src/qemu/qemu_command.c
+++ b/src/qemu/qemu_command.c
@@ -5519,6 +5519,9 @@ qemuBuildClockArgStr(virDomainClockDefPtr def)
         now += def->data.variable.adjustment;
         gmtime_r(&now, &nowbits);
 
+        /* Store the guest's basedate */
+        def->data.variable.basedate = now;
+
         virBufferAsprintf(&buf, "base=%d-%02d-%02dT%02d:%02d:%02d",
                           nowbits.tm_year + 1900,
                           nowbits.tm_mon + 1,

diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c
index fb625c94e77a75cc7cdca4d23a5407688248a7cd..c412ea257f3e56afab5372204273cead19800bd5 100644 (file)
--- a/src/qemu/qemu_process.c
+++ b/src/qemu/qemu_process.c
@@ -796,6 +796,19 @@ qemuProcessHandleRTCChange(qemuMonitorPtr mon ATTRIBUTE_UNUSED,
     virQEMUDriverConfigPtr cfg = virQEMUDriverGetConfig(driver);
 
     virObjectLock(vm);
+
+    /* QEMU's RTC_CHANGE event returns the offset from the specified
+     * date instead of the host UTC if a specific date is provided
+     * (-rtc base=$date). We need to convert it to be offset from
+     * host UTC.
+     */
+    if (vm->def->clock.offset == VIR_DOMAIN_CLOCK_OFFSET_VARIABLE) {
+        time_t now = time(NULL);
+
+        offset += vm->def->clock.data.variable.basedate -
+                  (unsigned long long)now;
+    }
+
     event = virDomainEventRTCChangeNewFromObj(vm, offset);
 
     if (vm->def->clock.offset == VIR_DOMAIN_CLOCK_OFFSET_VARIABLE)