diff -r f4cef1aa2521 xen/arch/x86/time.c
--- a/xen/arch/x86/time.c	Tue Mar 14 16:09:34 2006 +0100
+++ b/xen/arch/x86/time.c	Tue Mar 14 19:14:35 2006 +0100
@@ -286,6 +286,7 @@ static u64 pit_counter64;
 static u64 pit_counter64;
 static u16 pit_stamp;
 
+#define LATCH (((CLOCK_TICK_RATE)+(HZ/2))/HZ)
 static u16 pit_read_counter(void)
 {
     u16 count;
@@ -293,6 +294,32 @@ static u16 pit_read_counter(void)
     outb(0x80, PIT_MODE);
     count  = inb(PIT_CH2);
     count |= inb(PIT_CH2) << 8;
+
+    /* VIA686 Timer bug workaround
+       The timer sometimes looses it's programming, returning huge
+       counts. The delta counted should not be more than LATCH in
+       ideal world, but due to interrupt being disabled sometimes,
+       we can get longer intervals. Account for that by accepting
+       double the LATCH value.
+       To correct the error, we need to reset the counter. The
+       information about time elapsed is lost, so assume the interval
+       was LATCH long. This can make a slight difference in timer speed
+       if we were called from timer calibration code. It should not
+       be too much and it should be corrected on next callibration round.
+    */
+    if (pit_stamp - count > 2 * LATCH)
+    {
+        printk(KERN_WARNING "PIT Timer HW error: %u\n", pit_stamp - count);
+        /* reset the timer */
+        outb(0xb0, PIT_MODE);           /* binary, mode 0, LSB/MSB, Ch 2 */
+        outb(LATCH & 0xff, PIT_CH2);    /* LSB of count */
+        outb(LATCH >> 8, PIT_CH2);      /* MSB of count */
+        /* reset the stamp */
+        pit_stamp = LATCH;
+        /* correct the count returned to make LATCH difference */
+        count = 0;
+    }
+
     return count;
 }
 
@@ -315,6 +342,13 @@ static void init_pit(void)
 static void init_pit(void)
 {
     read_platform_count = read_pit_count;
+
+    /* setup the timer */
+    spin_lock_irq(&platform_timer_lock);
+    outb(0xb0, PIT_MODE);           /* binary, mode 0, LSB/MSB, Ch 2 */
+    outb(0, PIT_CH2);    /* LSB of count */
+    outb(0, PIT_CH2);      /* MSB of count */
+    spin_unlock_irq(&platform_timer_lock);
 
     pit_overflow();
     platform_timer_stamp = pit_counter64;