diff -r fc84efa61ef1 -r d42732f29bed xen/arch/x86/hvm/hvm.c
--- a/xen/arch/x86/hvm/hvm.c	Wed Feb 02 15:26:29 2011 -0600
+++ b/xen/arch/x86/hvm/hvm.c	Wed Feb 02 16:13:03 2011 -0600
@@ -2222,10 +2222,12 @@
         /* EBX value of main leaf 0 depends on enabled xsave features */
         if ( count == 0 && v->arch.xcr0 ) 
         {
-            for ( sub_leaf = 2; 
-                  (sub_leaf < 64) && (v->arch.xcr0 & (1ULL << sub_leaf));
-                  sub_leaf++ ) 
+            /* reset EBX to default value first */
+            *ebx = 576; 
+            for ( sub_leaf = 2; sub_leaf < 64; sub_leaf++ )
             {
+                if ( !(v->arch.xcr0 & (1ULL << sub_leaf)) )
+                    continue;
                 domain_cpuid(v->domain, input, sub_leaf, &_eax, &_ebx, &_ecx, 
                              &_edx);
                 if ( (_eax + _ebx) > *ebx )