1 files changed, 18 insertions, 4 deletions

diff --git a/init/calibrate.c b/init/calibrate.c
index f9000dfbe227..76ac9194cbc4 100644
--- a/init/calibrate.c
+++ b/init/calibrate.c
@@ -122,7 +122,7 @@ static unsigned long __cpuinit calibrate_delay_direct(void) {return 0;}
 static unsigned long __cpuinit calibrate_delay_converge(void)
 {
         /* First stage - slowly accelerate to find initial bounds */
-        unsigned long lpj, ticks, loopadd, chop_limit;
+        unsigned long lpj, lpj_base, ticks, loopadd, loopadd_base, chop_limit;
         int trials = 0, band = 0, trial_in_band = 0;
 
         lpj = (1<<12);
@@ -146,14 +146,18 @@ static unsigned long __cpuinit calibrate_delay_converge(void)
          * the largest likely undershoot. This defines our chop bounds.
          */
         trials -= band;
-        loopadd = lpj * band;
-        lpj *= trials;
-        chop_limit = lpj >> (LPS_PREC + 1);
+        loopadd_base = lpj * band;
+        lpj_base = lpj * trials;
+
+recalibrate:
+        lpj = lpj_base;
+        loopadd = loopadd_base;
 
         /*
          * Do a binary approximation to get lpj set to
          * equal one clock (up to LPS_PREC bits)
          */
+        chop_limit = lpj >> LPS_PREC;
         while (loopadd > chop_limit) {
                 lpj += loopadd;
                 ticks = jiffies;
@@ -165,6 +169,16 @@ static unsigned long __cpuinit calibrate_delay_converge(void)
                         lpj -= loopadd;
                 loopadd >>= 1;
         }
+        /*
+         * If we incremented every single time possible, presume we've
+         * massively underestimated initially, and retry with a higher
+         * start, and larger range. (Only seen on x86_64, due to SMIs)
+         */
+        if (lpj + loopadd * 2 == lpj_base + loopadd_base * 2) {
+                lpj_base = lpj;
+                loopadd_base <<= 2;
+                goto recalibrate;
+        }
 
         return lpj;
 }