bitkeeper revision 1.1348 (4266ef9bSWLiNFi-ZJ_TkK7jYaRikA)

Truly round off the div result to get right PIT frequency for guest. 
Otherwise, the guest's idea of time drifts away from that of the host.
 
Signed-off-by: Edwin Zhai <edwin.zhai@intel.com>
Signed-off-by: Arun Sharma <arun.sharma@intel.com>
Signed-off-by: ian@xensource.com

xen/include/xen/lib.h

@@ -23,7 +23,7 @@
 #define SWAP(_a, _b) \
    do { typeof(_a) _t = (_a); (_a) = (_b); (_b) = _t; } while ( 0 )
 
-#define DIV_ROUND(x, y) (((x) + (y) - 1) / (y))
+#define DIV_ROUND(x, y) (((x) + (y) / 2) / (y))
 
 #define reserve_bootmem(_p,_l) ((void)0)