From 6ee78d334a9e8e841880d6931892a8ebaa73faeb Mon Sep 17 00:00:00 2001
From: Michal Privoznik <mprivozn@redhat.com>
Date: Fri, 29 Apr 2016 18:01:39 +0200
Subject: [PATCH] qemu: Refresh RTC adjustment on qemuProcessReconnect

https://bugzilla.redhat.com/show_bug.cgi?id=1139766

Thing is, for some reasons you can have your domain's RTC to be
in something different than UTC. More weirdly, it's not only time
zone what you can shift it of, but an arbitrary value. So, if
domain is configured that way, libvirt will correctly put it onto
qemu cmd line and moreover track it as this offset changes during
domain's life time (e.g. because guest OS decides the best thing
to do is set new time to RTC). Anyway, they way in which this
tracking is implemented is events. But we've got a problem if
change in guest's RTC occurs and the daemon is not running. The
event is lost and we end up reporting invalid value in domain
XML. Therefore, when the daemon is starting up again and it is
reconnecting to all running domains, re-fetch their RTC so the
correct offset value can be computed.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
---
 src/qemu/qemu_process.c | 39 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)

diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c
index 527300aad0..348b3920df 100644
--- a/src/qemu/qemu_process.c
+++ b/src/qemu/qemu_process.c
@@ -1992,6 +1992,42 @@ qemuRefreshVirtioChannelState(virQEMUDriverPtr driver,
     return ret;
 }
 
+static void
+qemuRefreshRTC(virQEMUDriverPtr driver,
+               virDomainObjPtr vm)
+{
+    qemuDomainObjPrivatePtr priv = vm->privateData;
+    time_t now, then;
+    struct tm thenbits;
+    long localOffset;
+    int rv;
+
+    if (vm->def->clock.offset != VIR_DOMAIN_CLOCK_OFFSET_VARIABLE)
+        return;
+
+    memset(&thenbits, 0, sizeof(thenbits));
+    qemuDomainObjEnterMonitor(driver, vm);
+    now = time(NULL);
+    rv = qemuMonitorGetRTCTime(priv->mon, &thenbits);
+    if (qemuDomainObjExitMonitor(driver, vm) < 0)
+        rv = -1;
+
+    if (rv < 0)
+        return;
+
+    thenbits.tm_isdst = -1;
+    if ((then = mktime(&thenbits)) == (time_t) -1) {
+        virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+                       _("Unable to convert time"));
+        return;
+    }
+
+    /* Thing is, @now is in local TZ but @then in UTC. */
+    if (virTimeLocalOffsetFromUTC(&localOffset) < 0)
+        return;
+
+    vm->def->clock.data.variable.adjustment = then - now + localOffset;
+}
 
 int
 qemuProcessRefreshBalloonState(virQEMUDriverPtr driver,
@@ -3673,6 +3709,9 @@ qemuProcessReconnect(void *opaque)
     if (qemuRefreshVirtioChannelState(driver, obj) < 0)
         goto error;
 
+    /* If querying of guest's RTC failed, report error, but do not kill the domain. */
+    qemuRefreshRTC(driver, obj);
+
     if (qemuProcessRefreshBalloonState(driver, obj, QEMU_ASYNC_JOB_NONE) < 0)
         goto error;