diff -r 08e010c3f251 xen/arch/x86/bitops.c
--- a/xen/arch/x86/bitops.c	Tue Apr 15 16:39:00 2008 +0100
+++ b/xen/arch/x86/bitops.c	Wed Apr 16 09:38:06 2008 +0900
@@ -8,12 +8,15 @@ unsigned int __find_first_bit(
     unsigned long d0, d1, res;
 
     asm volatile (
-        "   xor %%eax,%%eax\n\t" /* also ensures ZF==1 if size==0 */
+        "1: xor %%eax,%%eax\n\t" /* also ensures ZF==1 if size==0 */
         "   repe; scas"__OS"\n\t"
-        "   je 1f\n\t"
+        "   je 2f\n\t"
         "   lea -"STR(BITS_PER_LONG/8)"(%2),%2\n\t"
-        "   bsf (%2),%0\n"
-        "1: sub %%ebx,%%edi\n\t"
+        "   bsf (%2),%0\n\t"
+        "   jnz 2f\n\t"
+        "   lea "STR(BITS_PER_LONG/8)"(%2),%2\n\t"
+        "   jmp 1b\n\t"
+        "2: sub %%ebx,%%edi\n\t"
         "   shl $3,%%edi\n\t"
         "   add %%edi,%%eax"
         : "=&a" (res), "=&c" (d0), "=&D" (d1)