Fix VMWare bug message to include information about the workaround

rr-debugger · Nov 5, 2015 · ca686c1 · ca686c1
1 parent c4e5fdb
commit ca686c1
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Showing 2 changed files with 9 additions and 3 deletions.
diff --git a/src/CPUIDBugDetector.cc b/src/CPUIDBugDetector.cc
@@ -32,9 +32,9 @@ static bool rcb_counts_ok(uint64_t prev, uint64_t current, const char* source) {
         "instructions\n"
         "    sometimes fails to be counted by the conditional branch "
         "performance\n"
-        "    counter. Partial workarounds have been enabled but replay may "
-        "diverge.\n"
-        "    Consider running rr not in a VMWare guest.\n"
+        "    counter. Work around this problem by adding\n"
+        "        monitor_control.disable_hvsim_clusters = true\n"
+        "    to your .vmx file.\n"
         "\n");
   }
   return false;

diff --git a/src/CPUIDBugDetector.h b/src/CPUIDBugDetector.h
@@ -10,6 +10,12 @@ class Task;
 /**
  * Helper to detect when the "CPUID can cause rcbs to be lost" bug is present.
  * See http://robert.ocallahan.org/2014/09/vmware-cpuid-conditional-branch.html
+ *
+ * This bug is caused by VMM optimizations described in
+ * https://www.usenix.org/system/files/conference/atc12/atc12-final158.pdf
+ * that cause instruction sequences related to CPUID to be optimized,
+ * eliminating the user-space execution of a conditional branch between two
+ * CPUID instructions (in some circumstances).
  */
 class CPUIDBugDetector {
 public: