diff -r c840095b9359 xen/common/schedule.c
--- a/xen/common/schedule.c	Mon Jul 26 03:55:45 2010 -0700
+++ b/xen/common/schedule.c	Mon Aug 16 18:33:07 2010 -0700
@@ -627,6 +627,30 @@ ret_t do_sched_op(int cmd, XEN_GUEST_HAN
         break;
     }
 
+    case SCHEDOP_yield_to:
+    {
+        struct sched_yield_to yld_s;
+        struct vcpu *vp;
+        struct domain *dp = current->domain;
+
+        ret = -EFAULT;
+        if ( copy_from_guest(&yld_s, arg, 1) )
+            break;
+
+        ret = -EINVAL;
+        if (is_idle_vcpu(current) || yld_s.vcpu_id > dp->max_vcpus)
+            break;
+
+        vp = dp->vcpu[yld_s.vcpu_id];
+        if (!vp->is_running) {
+            vcpu_kick(dp->vcpu[yld_s.vcpu_id]);
+            ret = do_yield();
+        } else
+            ret = 0;
+
+        break;
+    }
+
     case SCHEDOP_block:
     {
         ret = do_block();
diff -r c840095b9359 xen/include/public/sched.h
--- a/xen/include/public/sched.h	Mon Jul 26 03:55:45 2010 -0700
+++ b/xen/include/public/sched.h	Mon Aug 16 18:33:07 2010 -0700
@@ -108,6 +108,17 @@ DEFINE_XEN_GUEST_HANDLE(sched_remote_shu
 #define SHUTDOWN_suspend    2  /* Clean up, save suspend info, kill.         */
 #define SHUTDOWN_crash      3  /* Tell controller we've crashed.             */
 
+
+/*
+ *  * Voluntarily yield the CPU to another given vcpu
+ *   * @arg == vcpu info.
+ *    */
+#define SCHEDOP_yield_to      5
+struct sched_yield_to {
+    unsigned int version;
+    unsigned int vcpu_id;
+};
+
 #endif /* __XEN_PUBLIC_SCHED_H__ */
 
 /*