diff -r fa1ad484bf0b xen/arch/x86/hvm/hvm.c
--- a/xen/arch/x86/hvm/hvm.c	Wed Mar 31 14:28:31 2010 +0200
+++ b/xen/arch/x86/hvm/hvm.c	Wed Mar 31 16:13:59 2010 +0200
@@ -583,6 +583,24 @@ static int hvm_save_cpu_ctxt(struct doma
     return 0;
 }
 
+static int hvm_validate_efer(uint64_t value, uint64_t efer_validbits)
+{
+    if ( (value & ~efer_validbits) ||
+         ((sizeof(long) != 8) && (value & EFER_LME)) ||
+         (!cpu_has_nx && (value & EFER_NX)) ||
+         (!cpu_has_syscall && (value & EFER_SCE)) ||
+         (!cpu_has_ffxsr && (value & EFER_FFXSE)) )
+    {
+        return 1;
+    }
+
+    if ( efer_validbits & EFER_LMA )
+        if (( value & (EFER_LME|EFER_LMA)) == EFER_LMA )
+            return 1;
+
+    return 0;
+}
+
 static int hvm_load_cpu_ctxt(struct domain *d, hvm_domain_context_t *h)
 {
     int vcpuid, rc;
@@ -629,13 +647,8 @@ static int hvm_load_cpu_ctxt(struct doma
         return -EINVAL;
     }
 
-    if ( (ctxt.msr_efer & ~(EFER_FFXSE | EFER_LME | EFER_LMA |
-                            EFER_NX | EFER_SCE)) ||
-         ((sizeof(long) != 8) && (ctxt.msr_efer & EFER_LME)) ||
-         (!cpu_has_nx && (ctxt.msr_efer & EFER_NX)) ||
-         (!cpu_has_syscall && (ctxt.msr_efer & EFER_SCE)) ||
-         (!cpu_has_ffxsr && (ctxt.msr_efer & EFER_FFXSE)) ||
-         ((ctxt.msr_efer & (EFER_LME|EFER_LMA)) == EFER_LMA) )
+    if ( hvm_validate_efer(ctxt.msr_efer,
+             EFER_FFXSE | EFER_LME | EFER_LMA | EFER_NX | EFER_SCE) )
     {
         gdprintk(XENLOG_ERR, "HVM restore: bad EFER 0x%"PRIx64"\n",
                  ctxt.msr_efer);
@@ -984,11 +997,7 @@ int hvm_set_efer(uint64_t value)
 
     value &= ~EFER_LMA;
 
-    if ( (value & ~(EFER_FFXSE | EFER_LME | EFER_NX | EFER_SCE)) ||
-         ((sizeof(long) != 8) && (value & EFER_LME)) ||
-         (!cpu_has_nx && (value & EFER_NX)) ||
-         (!cpu_has_syscall && (value & EFER_SCE)) ||
-         (!cpu_has_ffxsr && (value & EFER_FFXSE)) )
+    if ( hvm_validate_efer(value, EFER_FFXSE | EFER_LME | EFER_NX | EFER_SCE) )
     {
         gdprintk(XENLOG_WARNING, "Trying to set reserved bit in "
                  "EFER: %"PRIx64"\n", value);