[hvm] Keep track of time offset between domain time and dom0 time.

On each rtc time update from the hvm domain, we send an ioreq request
to qemu which then updates the time offset xenstore entry.  The time
offset is preserved across reboot and can be set on domain creation
by setting the rtc_timeoffset variable in a config file.

From: Andrei Petrov <andrei.petrov@xensource.com>
Signed-off-by: Christian Limpach <Christian.Limpach@xensource.com>

tools/python/xen/xend/XendConfig.py

@@ -118,7 +118,7 @@ LEGACY_CFG_TO_XENAPI_CFG = reverse_dict(XENAPI_CFG_TO_LEGACY_CFG)
 # Platform configuration keys.
 XENAPI_PLATFORM_CFG = [ 'acpi', 'apic', 'boot', 'device_model', 'display', 
                         'fda', 'fdb', 'keymap', 'isa', 'localtime',
-                        'nographic', 'pae', 'serial', 'sdl',
+                        'nographic', 'pae', 'rtc_timeoffset', 'serial', 'sdl',
                         'soundhw','stdvga', 'usb', 'usbdevice', 'vnc',
                         'vncconsole', 'vncdisplay', 'vnclisten',
                         'vncpasswd', 'vncunused', 'xauthority']
@@ -203,6 +203,7 @@ LEGACY_CFG_TYPES = {
     'on_xend_stop':  str,
     'on_xend_start': str,
     'online_vcpus':  int,
+    'rtc/timeoffset': str,
 }
 
 # Values that should be stored in xenstore's /vm/<uuid> that is used

tools/python/xen/xend/XendDomainInfo.py

@@ -859,7 +859,8 @@ class XendDomainInfo:
         # Check whether values in the configuration have
         # changed in Xenstore.
         
-        cfg_vm = ['name', 'on_poweroff', 'on_reboot', 'on_crash']
+        cfg_vm = ['name', 'on_poweroff', 'on_reboot', 'on_crash',
+                  'rtc/timeoffset']
         
         vm_details = self._readVMDetails([(k,XendConfig.LEGACY_CFG_TYPES[k])
                                            for k in cfg_vm])
@@ -888,6 +889,11 @@ class XendDomainInfo:
             self.info.update_with_image_sxp(sxp.from_string(image_sxp))
             changed = True
 
+        # Check if the rtc offset has changes
+        if vm_details.get("rtc/timeoffset", 0) != self.info["platform"].get("rtc_timeoffset", 0):
+            self.info["platform"]["rtc_timeoffset"] = vm_details.get("rtc/timeoffset", 0)
+            changed = True
+ 
         if changed:
             # Update the domain section of the store, as this contains some
             # parameters derived from the VM configuration.

tools/python/xen/xend/image.py

@@ -256,9 +256,12 @@ class HVMImageHandler(ImageHandler):
         self.xauthority = vmConfig['platform'].get('xauthority')
         self.vncconsole = vmConfig['platform'].get('vncconsole')
 
+        rtc_timeoffset = vmConfig['platform'].get('rtc_timeoffset')
+
         self.vm.storeVm(("image/dmargs", " ".join(self.dmargs)),
                         ("image/device-model", self.device_model),
                         ("image/display", self.display))
+        self.vm.storeVm(("rtc/timeoffset", rtc_timeoffset))
 
         self.pid = None
 

tools/python/xen/xm/create.py

@@ -186,6 +186,10 @@ gopts.var('cpus', val='CPUS',
           fn=set_value, default=None,
           use="CPUS to run the domain on.")
 
+gopts.var('rtc_timeoffset', val='RTC_TIMEOFFSET',
+          fn=set_value, default="0",
+          use="Set RTC offset.")
+
 gopts.var('pae', val='PAE',
           fn=set_int, default=1,
           use="Disable or enable PAE of HVM domain.")
@@ -717,7 +721,7 @@ def configure_hvm(config_image, vals):
     args = [ 'device_model', 'pae', 'vcpus', 'boot', 'fda', 'fdb',
              'localtime', 'serial', 'stdvga', 'isa', 'nographic', 'soundhw',
              'vnc', 'vncdisplay', 'vncunused', 'vncconsole', 'vnclisten',
-             'sdl', 'display', 'xauthority',
+             'sdl', 'display', 'xauthority', 'rtc_timeoffset',
              'acpi', 'apic', 'usb', 'usbdevice', 'keymap' ]
     for a in args:
         if a in vals.__dict__ and vals.__dict__[a] is not None: