Fix the issue: Dom0-S3 will fail after sleep-wake for several times.
  -Time zone info just needs to be calculated in S3 suspend procedure.
   However, time_suspend() is also called on AP. That wasteful 
   get_cmos_time() on AP may break __cpu_die() assumption since 
   get_cmos_time() can take up to one second. This fix just limits 
   it on BSP.

Improve accuracy of the cmos_utc_offset calculation.
  -The get_cmos_time() function may take up to 1 second, while execution
   of the NOW() macro could be very fast. So when calculating 
   cmos_utc_offset, get_cmos_time() should be firstly executed, and then
   (wc_sec + (wc_nsec + NOW()) / 1000000000ULL). This would make the 
   calculation more accuracy than vice versa.

Signed-off-by: Xu Dongxiao <dongxiao.xu@intel.com>

diff -r 56b42d68518e xen/arch/x86/time.c
--- a/xen/arch/x86/time.c	Thu Jan 10 22:53:43 2008 +0000
+++ b/xen/arch/x86/time.c	Fri Jan 25 10:15:07 2008 +0800
@@ -976,8 +976,11 @@ static long cmos_utc_offset; /* in secon
 
 int time_suspend(void)
 {
-    cmos_utc_offset = (wc_sec + (wc_nsec + NOW()) / 1000000000ULL)
-        - get_cmos_time();
+    if ( smp_processor_id() == 0 )
+    {
+        cmos_utc_offset = -get_cmos_time();
+        cmos_utc_offset += (wc_sec + (wc_nsec + NOW()) / 1000000000ULL);
+    }
 
     /* Better to cancel calibration timer for accuracy. */
     kill_timer(&this_cpu(cpu_time).calibration_timer);