Index: /trunk/src/VBox/VMM/VMMR3/CPUMR3CpuId.cpp
===================================================================
--- /trunk/src/VBox/VMM/VMMR3/CPUMR3CpuId.cpp	(revision 80659)
+++ /trunk/src/VBox/VMM/VMMR3/CPUMR3CpuId.cpp	(revision 80660)
@@ -4740,4 +4740,10 @@
             pVM->cpum.s.GuestFeatures.fLongMode = 1;
             pVM->cpum.s.GuestFeatures.cVmxMaxPhysAddrWidth = pVM->cpum.s.GuestFeatures.cMaxPhysAddrWidth;
+            if (pVM->cpum.s.GuestFeatures.fVmx)
+                for (VMCPUID idCpu = 0; idCpu < pVM->cCpus; idCpu++)
+                {
+                    PVMCPU pVCpu = pVM->apCpusR3[idCpu];
+                    pVCpu->cpum.s.Guest.hwvirt.vmx.Msrs.u64Basic &= ~VMX_BASIC_PHYSADDR_WIDTH_32BIT;
+                }
             LogRel(("CPUM: SetGuestCpuIdFeature: Enabled LONG MODE\n"));
             break;
@@ -5060,4 +5066,10 @@
             pVM->cpum.s.GuestFeatures.fLongMode = 0;
             pVM->cpum.s.GuestFeatures.cVmxMaxPhysAddrWidth = 32;
+            if (pVM->cpum.s.GuestFeatures.fVmx)
+                for (VMCPUID idCpu = 0; idCpu < pVM->cCpus; idCpu++)
+                {
+                    PVMCPU pVCpu = pVM->apCpusR3[idCpu];
+                    pVCpu->cpum.s.Guest.hwvirt.vmx.Msrs.u64Basic |= VMX_BASIC_PHYSADDR_WIDTH_32BIT;
+                }
             break;