4 files changed, 59 insertions, 32 deletions

diff --git a/src/sim/SConscript b/src/sim/SConscript
index 0b3a35915..204bfca3b 100644
--- a/src/sim/SConscript
+++ b/src/sim/SConscript
@@ -42,6 +42,7 @@ SimObject('SubSystem.py')
 Source('arguments.cc')
 Source('async.cc')
 Source('core.cc')
+Source('tags.cc')
 Source('cxx_config.cc')
 Source('cxx_manager.cc')
 Source('cxx_config_ini.cc')
diff --git a/src/sim/root.cc b/src/sim/root.cc
index 1d58c3bbe..7647ca5b7 100644
--- a/src/sim/root.cc
+++ b/src/sim/root.cc
@@ -132,8 +132,6 @@ Root::loadState(CheckpointIn &cp)
 void
 Root::serialize(CheckpointOut &cp) const
 {
-    uint64_t cpt_ver = gem5CheckpointVersion;
-    SERIALIZE_SCALAR(cpt_ver);
     SERIALIZE_SCALAR(FullSystem);
     std::string isa = THE_ISA_STR;
     SERIALIZE_SCALAR(isa);
@@ -141,27 +139,7 @@ Root::serialize(CheckpointOut &cp) const
 
 void
 Root::unserialize(CheckpointIn &cp)
-{
-    uint64_t cpt_ver = 0;
-    UNSERIALIZE_OPT_SCALAR(cpt_ver);
-    if (cpt_ver < gem5CheckpointVersion) {
-        warn("**********************************************************\n");
-        warn("!!!! Checkpoint ver %#x is older than current ver %#x !!!!\n",
-                cpt_ver, gem5CheckpointVersion);
-        warn("You might experience some issues when restoring and should run "
-             "the checkpoint upgrader (util/cpt_upgrader.py) on your "
-             "checkpoint\n");
-        warn("**********************************************************\n");
-    } else if (cpt_ver > gem5CheckpointVersion) {
-        warn("**********************************************************\n");
-        warn("!!!! Checkpoint ver %#x is newer than current ver %#x !!!!\n",
-                cpt_ver, gem5CheckpointVersion);
-        warn("Running a new checkpoint with an older version of gem5 is not "
-             "supported. While it might work, you may experience incorrect "
-             "behavior or crashes.\n");
-        warn("**********************************************************\n");
-     }
-}
+{}
 
 
 bool FullSystem;
diff --git a/src/sim/serialize.cc b/src/sim/serialize.cc
index 0904b1375..f9a945b95 100644
--- a/src/sim/serialize.cc
+++ b/src/sim/serialize.cc
@@ -496,16 +496,73 @@ class Globals : public Serializable
 /// The one and only instance of the Globals class.
 Globals globals;
 
+/// The version tags for this build of the simulator, to be stored in the
+/// Globals section during serialization and compared upon unserialization.
+extern std::set<std::string> version_tags;
+
 void
 Globals::serialize(CheckpointOut &cp) const
 {
     paramOut(cp, "curTick", curTick());
+    SERIALIZE_CONTAINER(version_tags);
 }
 
 void
 Globals::unserialize(CheckpointIn &cp)
 {
     paramIn(cp, "curTick", unserializedCurTick);
+
+    const std::string &section(Serializable::currentSection());
+    std::string str;
+    if (!cp.find(section, "version_tags", str)) {
+        warn("**********************************************************\n");
+        warn("!!!! Checkpoint uses an old versioning scheme.        !!!!\n");
+        warn("Run the checkpoint upgrader (util/cpt_upgrader.py) on your "
+             "checkpoint\n");
+        warn("**********************************************************\n");
+        return;
+    }
+
+    std::set<std::string> cpt_tags;
+    arrayParamIn(cp, "version_tags", cpt_tags); // UNSERIALIZE_CONTAINER
+
+    bool err = false;
+    for (const auto& t : version_tags) {
+        if (cpt_tags.find(t) == cpt_tags.end()) {
+            // checkpoint is missing tag that this binary has
+            if (!err) {
+                warn("*****************************************************\n");
+                warn("!!!! Checkpoint is missing the following version tags:\n");
+                err = true;
+            }
+            warn("  %s\n", t);
+        }
+    }
+    if (err) {
+        warn("You might experience some issues when restoring and should run "
+             "the checkpoint upgrader (util/cpt_upgrader.py) on your "
+             "checkpoint\n");
+        warn("**********************************************************\n");
+    }
+
+    err = false;
+    for (const auto& t : cpt_tags) {
+        if (version_tags.find(t) == version_tags.end()) {
+            // gem5 binary is missing tag that this checkpoint has
+            if (!err) {
+                warn("*****************************************************\n");
+                warn("!!!! gem5 is missing the following version tags:\n");
+                err = true;
+            }
+            warn("  %s\n", t);
+        }
+    }
+    if (err) {
+        warn("Running a checkpoint with incompatible version tags is not "
+             "supported. While it might work, you may experience incorrect "
+             "behavior or crashes.\n");
+        warn("**********************************************************\n");
+     }
 }
 
 Serializable::Serializable()
diff --git a/src/sim/serialize.hh b/src/sim/serialize.hh
index 4a2cc04e9..9a1170a9e 100644
--- a/src/sim/serialize.hh
+++ b/src/sim/serialize.hh
@@ -71,15 +71,6 @@ class EventQueue;
 typedef std::ostream CheckpointOut;
 
 
-/** The current version of the checkpoint format.
- * This should be incremented by 1 and only 1 for every new version, where a new
- * version is defined as a checkpoint created before this version won't work on
- * the current version until the checkpoint format is updated. Adding a new
- * SimObject shouldn't cause the version number to increase, only changes to
- * existing objects such as serializing/unserializing more state, changing sizes
- * of serialized arrays, etc. */
-static const uint64_t gem5CheckpointVersion = 0x000000000000000f;
-
 template <class T>
 void paramOut(CheckpointOut &cp, const std::string &name, const T &param);