Index: /trunk/src/VBox/VMM/VMMAll/GIMAllHv.cpp
===================================================================
--- /trunk/src/VBox/VMM/VMMAll/GIMAllHv.cpp	(revision 57998)
+++ /trunk/src/VBox/VMM/VMMAll/GIMAllHv.cpp	(revision 57999)
@@ -413,6 +413,11 @@
             if (pHv->fIsVendorMsHv)
             {
+#ifndef IN_RING_3
+                return VINF_CPUM_R3_MSR_READ;
+#else
+                LogRelMax(1, ("GIM: HyperV: Guest querying debug options MSR, returning %#x\n", GIM_HV_DEBUG_OPTIONS_MSR_ENABLE));
                 *puValue = GIM_HV_DEBUG_OPTIONS_MSR_ENABLE;
                 return VINF_SUCCESS;
+#endif
             }
             return VERR_CPUM_RAISE_GP_0;
@@ -632,5 +637,12 @@
         {
             if (pHv->fIsVendorMsHv)
+            {
+#ifndef IN_RING_3
+                return VINF_CPUM_R3_MSR_WRITE;
+#else
+                LogRelMax(1, ("GIM: HyperV: Guest setting debug options MSR to %#RX64, ignoring\n", uRawValue));
                 return VINF_SUCCESS;
+#endif
+            }
             return VERR_CPUM_RAISE_GP_0;
         }
Index: /trunk/src/VBox/VMM/VMMR3/GIMHv.cpp
===================================================================
--- /trunk/src/VBox/VMM/VMMR3/GIMHv.cpp	(revision 57998)
+++ /trunk/src/VBox/VMM/VMMR3/GIMHv.cpp	(revision 57999)
@@ -116,4 +116,5 @@
     if (!RTStrNCmp(szVendor, GIM_HV_VENDOR_MICROSOFT, sizeof(GIM_HV_VENDOR_MICROSOFT) - 1))
         pHv->fIsVendorMsHv = true;
+    LogRel(("GIM: HyperV: Reporting vendor ID as '%s'\n", szVendor));
 
     /*