1 files changed, 20 insertions, 14 deletions

diff --git a/arch/x86/kernel/tsc_32.c b/arch/x86/kernel/tsc_32.c
index f04d08a7d022..9ebc0dab66b4 100644
--- a/arch/x86/kernel/tsc_32.c
+++ b/arch/x86/kernel/tsc_32.c
@@ -137,31 +137,37 @@ unsigned long native_calculate_cpu_khz(void)
 
         local_irq_save(flags);
 
-        /* run 3 times to ensure the cache is warm */
+        /* run 3 times to ensure the cache is warm and to get an accurate reading */
         for (i = 0; i < 3; i++) {
                 mach_prepare_counter();
                 rdtscll(start);
                 mach_countup(&count);
                 rdtscll(end);
+
+                /*
+                 * Error: ECTCNEVERSET
+                 * The CTC wasn't reliable: we got a hit on the very first read,
+                 * or the CPU was so fast/slow that the quotient wouldn't fit in
+                 * 32 bits..
+                 */
+                if (count <= 1)
+                        continue;
+
+                /* cpu freq too slow: */
+                if ((end - start) <= CALIBRATE_TIME_MSEC)
+                        continue;
+
+                /*
+                 * We want the minimum time of all runs in case one of them
+                 * is inaccurate due to SMI or other delay
+                 */
                 delta64 = min(delta64, (end - start));
         }
-        /*
-         * Error: ECTCNEVERSET
-         * The CTC wasn't reliable: we got a hit on the very first read,
-         * or the CPU was so fast/slow that the quotient wouldn't fit in
-         * 32 bits..
-         */
-        if (count <= 1)
-                goto err;
 
-        /* cpu freq too fast: */
+        /* cpu freq too fast (or every run was bad): */
         if (delta64 > (1ULL<<32))
                 goto err;
 
-        /* cpu freq too slow: */
-        if (delta64 <= CALIBRATE_TIME_MSEC)
-                goto err;
-
         delta64 += CALIBRATE_TIME_MSEC/2; /* round for do_div */
         do_div(delta64,CALIBRATE_TIME_MSEC);