Make dom0_enforce_cpus() use vcpu_hotplug rather than directly modifying the sysfs entries.

Directly modifying the sysfs entries causes the xenstore state of
a cpu's availability to be incorrect.  Also slightly modify the
dom0-cpus description in the xend-config.  Rather than specifying which
dom0 vcpus are to be used, it is now a target of how many vcpus to use
as pinvcpu ops are the preferred method for setting which physical cpu a
vcpu uses.
Signed-off-by: Ryan Harper <ryanh@us.ibm.com>
Signed-off-by: Christian Limpach <Christian.Limpach@cl.cam.ac.uk>

tools/python/xen/xend/XendDomain.py

@@ -155,6 +155,7 @@ class XendDomain:
         if not dom0:
             dom0 = self.domain_unknown(0)
         dom0.dom0_init_store()    
+        dom0.dom0_enforce_cpus()
 
     def close(self):
         pass

tools/python/xen/xend/XendDomainInfo.py

@@ -1120,6 +1120,26 @@ class XendDomainInfo:
             # get run-time value of vcpus and update store
             self.configure_vcpus(dom_get(self.domid)['vcpus'])
 
+    def dom0_enforce_cpus(self):
+        dom = 0
+        # get max number of cpus to use for dom0 from config
+        from xen.xend import XendRoot
+        xroot = XendRoot.instance()
+        target = int(xroot.get_dom0_cpus())
+        log.debug("number of cpus to use is %d" % (target))
+   
+        # target = 0 means use all processors
+        if target > 0:
+            # count the number of online vcpus (cpu values in v2c map >= 0)
+            vcpu_to_cpu = dom_get(dom)['vcpu_to_cpu']
+            vcpus_online = len(filter(lambda x: x >= 0, vcpu_to_cpu))
+            log.debug("found %d vcpus online" % (vcpus_online))
+
+            # disable any extra vcpus that are online over the requested target
+            for vcpu in range(target, vcpus_online):
+                log.info("enforcement is disabling DOM%d VCPU%d" % (dom, vcpu))
+                self.vcpu_hotplug(vcpu, 0)
+
 
 def vm_field_ignore(_, _1, _2, _3):
     """Dummy config field handler used for fields with built-in handling.

tools/python/xen/xend/server/SrvDaemon.py

@@ -298,7 +298,6 @@ class Daemon:
         return self.cleanup(kill=True)
 
     def run(self, status):
-        _enforce_dom0_cpus()
         try:
             log.info("Xend Daemon started")
             event.listenEvent(self)
@@ -323,32 +322,6 @@ class Daemon:
         #sys.exit(rc)
         os._exit(rc)
 
-def _enforce_dom0_cpus():
-    dn = xroot.get_dom0_cpus()
-
-    for d in glob.glob("/sys/devices/system/cpu/cpu*"):
-        cpu = int(os.path.basename(d)[3:])
-        if (dn == 0) or (cpu < dn):
-            v = "1"
-        else:
-            v = "0"
-        try:
-            f = open("%s/online" %d, "r+")
-            c = f.read(1)
-            if (c != v):
-                if v == "0":
-                    log.info("dom0 is trying to give back cpu %d", cpu)
-                else:
-                    log.info("dom0 is trying to take cpu %d", cpu)
-                f.seek(0)
-                f.write(v)
-                f.close()
-                log.info("dom0 successfully enforced cpu %d", cpu)
-            else:
-                f.close()
-        except:
-            pass
-
 def instance():
     global inst
     try: