diff -r 483d006cc607 tools/libxc/xc_cpuid_x86.c
--- a/tools/libxc/xc_cpuid_x86.c	Fri Apr 25 13:46:27 2008 +0100
+++ b/tools/libxc/xc_cpuid_x86.c	Wed Apr 30 16:18:53 2008 +0100
@@ -385,7 +385,10 @@ int xc_cpuid_set(
     for ( i = 0; i < 4; i++ )
     {
         if ( config[i] == NULL )
+        {
+            regs[i] = polregs[i];
             continue;
+        }
         
         config_transformed[i] = alloc_str();
 
diff -r 483d006cc607 tools/python/xen/lowlevel/xc/xc.c
--- a/tools/python/xen/lowlevel/xc/xc.c	Fri Apr 25 13:46:27 2008 +0100
+++ b/tools/python/xen/lowlevel/xc/xc.c	Wed Apr 30 16:18:53 2008 +0100
@@ -696,7 +696,7 @@ static PyObject *pyxc_dom_set_cpuid(XcOb
     unsigned int input[2];
     char *regs[4], *regs_transform[4];
 
-    if ( !PyArg_ParseTuple(args, "iiOO", &domid,
+    if ( !PyArg_ParseTuple(args, "IIOO", &domid,
                            &input[0], &sub_input, &config) )
         return NULL;
 
diff -r 483d006cc607 tools/python/xen/xm/create.py
--- a/tools/python/xen/xm/create.py	Fri Apr 25 13:46:27 2008 +0100
+++ b/tools/python/xen/xm/create.py	Wed Apr 30 16:18:53 2008 +0100
@@ -856,7 +856,9 @@ def preprocess_cpuid(vals, attr_name):
     if not vals.cpuid: return
     cpuid = {} 
     for cpuid_input in getattr(vals, attr_name):
-        cpuid_match = re.match(r"(?P<input>(0x)?[0-9A-Fa-f]+):(?P<regs>.*)", cpuid_input)
+        input_re = "(0x)?[0-9A-Fa-f]+(,(0x)?[0-9A-Fa-f]+)?"
+        cpuid_match = re.match(r'(?P<input>%s):(?P<regs>.*)' % \
+                               input_re, cpuid_input)
         if cpuid_match != None:
             res_cpuid = cpuid_match.groupdict()
             input = res_cpuid['input']