diff -r 1f466caea5b7 xen/arch/x86/hvm/svm/asid.c
--- a/xen/arch/x86/hvm/svm/asid.c	Fri Jun 08 15:24:29 2012 +0200
+++ b/xen/arch/x86/hvm/svm/asid.c	Tue Jun 12 15:12:48 2012 +0200
@@ -63,7 +63,8 @@ void svm_asid_handle_vmrun(void)
         return;
     }
 
-    vmcb_set_guest_asid(vmcb, p_asid->asid);
+    if (vmcb_get_guest_asid(vmcb) != p_asid->asid)
+        vmcb_set_guest_asid(vmcb, p_asid->asid);
     vmcb->tlb_control = need_flush;
 }