sim: revamp unserialization procedure

Replace direct call to unserialize() on each SimObject with a pair of
calls for better control over initialization in both ckpt and non-ckpt
cases.

If restoring from a checkpoint, loadState(ckpt) is called on each
SimObject.  The default implementation simply calls unserialize() if
there is a corresponding checkpoint section, so we get backward
compatibility for existing objects.  However, objects can override
loadState() to get other behaviors, e.g., doing other programmed
initializations after unserialize(), or complaining if no checkpoint
section is found.  (Note that the default warning for a missing
checkpoint section is now gone.)

If not restoring from a checkpoint, we call the new initState() method
on each SimObject instead.  This provides a hook for state
initializations that are only required when *not* restoring from a
checkpoint.

Given this new framework, do some cleanup of LiveProcess subclasses
and X86System, which were (in some cases) emulating initState()
behavior in startup via a local flag or (in other cases) erroneously
doing initializations in startup() that clobbered state loaded earlier
by unserialize().

src/arch/alpha/process.cc

@@ -173,19 +173,35 @@ AlphaLiveProcess::argsInit(int intSize, int pageSize)
 }
 
 void
-AlphaLiveProcess::startup()
+AlphaLiveProcess::setupASNReg()
 {
     ThreadContext *tc = system->getThreadContext(contextIds[0]);
     tc->setMiscRegNoEffect(IPR_DTB_ASN, M5_pid << 57);
+}
 
-    if (checkpointRestored) {
-        return;
-    }
 
-    Process::startup();
+void
+AlphaLiveProcess::loadState(Checkpoint *cp)
+{
+    LiveProcess::loadState(cp);
+    // need to set up ASN after unserialization since M5_pid value may
+    // come from checkpoint
+    setupASNReg();
+}
+
+
+void
+AlphaLiveProcess::initState()
+{
+    // need to set up ASN before further initialization since init
+    // will involve writing to virtual memory addresses
+    setupASNReg();
+
+    LiveProcess::initState();
 
     argsInit(MachineBytes, VMPageSize);
 
+    ThreadContext *tc = system->getThreadContext(contextIds[0]);
     tc->setIntReg(GlobalPointerReg, objFile->globalPointer());
     //Operate in user mode
     tc->setMiscRegNoEffect(IPR_ICM, 0x18);

src/arch/alpha/process.hh

@@ -36,10 +36,14 @@
 
 class AlphaLiveProcess : public LiveProcess
 {
+  private:
+    void setupASNReg();
+
   protected:
     AlphaLiveProcess(LiveProcessParams *params, ObjectFile *objFile);
 
-    void startup();
+    void loadState(Checkpoint *cp);
+    void initState();
 
     void argsInit(int intSize, int pageSize);
 

src/arch/arm/process.cc

@@ -76,6 +76,7 @@ ArmLiveProcess::ArmLiveProcess(LiveProcessParams *params, ObjectFile *objFile,
 void
 ArmLiveProcess::startup()
 {
+    LiveProcess::startup();
     argsInit(MachineBytes, VMPageSize);
 }
 
@@ -114,9 +115,6 @@ ArmLiveProcess::argsInit(int intSize, int pageSize)
     //We want 16 byte alignment
     uint64_t align = 16;
 
-    // Overloaded argsInit so that we can fine-tune for ARM architecture
-    Process::startup();
-
     // load object file into target memory
     objFile->loadSections(initVirtMem);
 

src/arch/mips/process.cc

@@ -67,9 +67,9 @@ MipsLiveProcess::MipsLiveProcess(LiveProcessParams * params,
 }
 
 void
-MipsLiveProcess::startup()
+MipsLiveProcess::initState()
 {
-    Process::startup();
+    LiveProcess::initState();
 
     argsInit<uint32_t>(VMPageSize);
 }
@@ -79,7 +79,6 @@ void
 MipsLiveProcess::argsInit(int pageSize)
 {
     int intSize = sizeof(IntType);
-    Process::startup();
 
     // load object file into target memory
     objFile->loadSections(initVirtMem);

src/arch/mips/process.hh

@@ -45,7 +45,7 @@ class MipsLiveProcess : public LiveProcess
   protected:
     MipsLiveProcess(LiveProcessParams * params, ObjectFile *objFile);
 
-    void startup();
+    void initState();
 
     template<class IntType>
     void argsInit(int pageSize);

src/arch/power/linux/process.cc

@@ -432,9 +432,9 @@ PowerLinuxProcess::getDesc(int callnum)
 }
 
 void
-PowerLinuxProcess::startup()
+PowerLinuxProcess::initState()
 {
-    PowerLiveProcess::startup();
+    PowerLiveProcess::initState();
 }
 
 PowerISA::IntReg

src/arch/power/linux/process.hh

@@ -44,7 +44,7 @@ class PowerLinuxProcess : public PowerLiveProcess
 
     virtual SyscallDesc* getDesc(int callnum);
 
-    void startup();
+    void initState();
 
     PowerISA::IntReg getSyscallArg(ThreadContext *tc, int &i);
     void setSyscallArg(ThreadContext *tc, int i, PowerISA::IntReg val);

src/arch/power/process.cc

@@ -63,8 +63,10 @@ PowerLiveProcess::PowerLiveProcess(LiveProcessParams *params,
 }
 
 void
-PowerLiveProcess::startup()
+PowerLiveProcess::initState()
 {
+    Process::initState();
+
     argsInit(MachineBytes, VMPageSize);
 }
 
@@ -83,9 +85,6 @@ PowerLiveProcess::argsInit(int intSize, int pageSize)
     //We want 16 byte alignment
     uint64_t align = 16;
 
-    // Overloaded argsInit so that we can fine-tune for POWER architecture
-    Process::startup();
-
     // load object file into target memory
     objFile->loadSections(initVirtMem);
 

src/arch/power/process.hh

@@ -46,7 +46,7 @@ class PowerLiveProcess : public LiveProcess
   protected:
     PowerLiveProcess(LiveProcessParams * params, ObjectFile *objFile);
 
-    void startup();
+    void initState();
 
   public:
     void argsInit(int intSize, int pageSize);

src/arch/sparc/process.cc

@@ -111,9 +111,9 @@ void SparcLiveProcess::handleTrap(int trapNum, ThreadContext *tc)
 }
 
 void
-SparcLiveProcess::startup()
+SparcLiveProcess::initState()
 {
-    Process::startup();
+    LiveProcess::initState();
 
     ThreadContext *tc = system->getThreadContext(contextIds[0]);
     //From the SPARC ABI
@@ -157,12 +157,9 @@ SparcLiveProcess::startup()
 }
 
 void
-Sparc32LiveProcess::startup()
+Sparc32LiveProcess::initState()
 {
-    if (checkpointRestored)
-        return;
-
-    SparcLiveProcess::startup();
+    SparcLiveProcess::initState();
 
     ThreadContext *tc = system->getThreadContext(contextIds[0]);
     //The process runs in user mode with 32 bit addresses
@@ -172,12 +169,9 @@ Sparc32LiveProcess::startup()
 }
 
 void
-Sparc64LiveProcess::startup()
+Sparc64LiveProcess::initState()
 {
-    if (checkpointRestored)
-        return;
-
-    SparcLiveProcess::startup();
+    SparcLiveProcess::initState();
 
     ThreadContext *tc = system->getThreadContext(contextIds[0]);
     //The process runs in user mode

src/arch/sparc/process.hh

@@ -52,7 +52,7 @@ class SparcLiveProcess : public LiveProcess
     SparcLiveProcess(LiveProcessParams * params,
             ObjectFile *objFile, Addr _StackBias);
 
-    void startup();
+    void initState();
 
     template<class IntType>
     void argsInit(int pageSize);
@@ -87,7 +87,7 @@ class Sparc32LiveProcess : public SparcLiveProcess
         mmap_start = mmap_end = 0x70000000;
     }
 
-    void startup();
+    void initState();
 
   public:
 
@@ -115,7 +115,7 @@ class Sparc64LiveProcess : public SparcLiveProcess
         mmap_start = mmap_end = 0xfffff80000000000ULL;
     }
 
-    void startup();
+    void initState();
 
   public:
 

src/arch/x86/linux/system.cc

@@ -59,9 +59,9 @@ LinuxX86System::~LinuxX86System()
 }
 
 void
-LinuxX86System::startup()
+LinuxX86System::initState()
 {
-    X86System::startup();
+    X86System::initState();
 
     // The location of the real mode data structure.
     const Addr realModeData = 0x90200;

src/arch/x86/linux/system.hh

@@ -58,7 +58,7 @@ class LinuxX86System : public X86System
     LinuxX86System(Params *p);
     ~LinuxX86System();
 
-    void startup();
+    void initState();
 };
 
 #endif

src/arch/x86/process.cc

@@ -157,12 +157,9 @@ X86LiveProcess::getDesc(int callnum)
 }
 
 void
-X86_64LiveProcess::startup()
+X86_64LiveProcess::initState()
 {
-    LiveProcess::startup();
-
-    if (checkpointRestored)
-        return;
+    X86LiveProcess::initState();
 
     argsInit(sizeof(uint64_t), VMPageSize);
 
@@ -255,12 +252,9 @@ X86_64LiveProcess::startup()
 }
 
 void
-I386LiveProcess::startup()
+I386LiveProcess::initState()
 {
-    LiveProcess::startup();
-
-    if (checkpointRestored)
-        return;
+    X86LiveProcess::initState();
 
     argsInit(sizeof(uint32_t), VMPageSize);
 

src/arch/x86/process.hh

@@ -99,7 +99,7 @@ namespace X86ISA
 
       public:
         void argsInit(int intSize, int pageSize);
-        void startup();
+        void initState();
 
         X86ISA::IntReg getSyscallArg(ThreadContext *tc, int &i);
         void setSyscallArg(ThreadContext *tc, int i, X86ISA::IntReg val);
@@ -123,7 +123,7 @@ namespace X86ISA
 
       public:
         void argsInit(int intSize, int pageSize);
-        void startup();
+        void initState();
 
         void syscall(int64_t callnum, ThreadContext *tc);
         X86ISA::IntReg getSyscallArg(ThreadContext *tc, int &i);

src/arch/x86/system.cc

@@ -109,9 +109,10 @@ installSegDesc(ThreadContext *tc, SegmentRegIndex seg,
 }
 
 void
-X86System::startup()
+X86System::initState()
 {
-    System::startup();
+    System::initState();
+
     ThreadContext *tc = threadContexts[0];
     // This is the boot strap processor (BSP). Initialize it to look like
     // the boot loader has just turned control over to the 64 bit OS. We

src/arch/x86/system.hh

@@ -77,7 +77,7 @@ class X86System : public System
     void serialize(std::ostream &os);
     void unserialize(Checkpoint *cp, const std::string &section);
 
-    void startup();
+    void initState();
 
   protected:
 

src/python/m5/simulate.py

@@ -88,8 +88,12 @@ def instantiate(ckpt_dir=None):
 
     # Restore checkpoint (if any)
     if ckpt_dir:
-        internal.core.unserializeAll(ckpt_dir)
+        ckpt = internal.core.getCheckpoint(ckpt_dir)
+        internal.core.unserializeGlobals(ckpt);
+        for obj in root.descendants(): obj.loadState(ckpt)
         need_resume.append(root)
+    else:
+        for obj in root.descendants(): obj.initState()
 
     # Reset to put the stats in a consistent state.
     stats.reset()

src/python/swig/core.i

@@ -75,8 +75,11 @@ void setClockFrequency(Tick ticksPerSecond);
 %immutable curTick;
 Tick curTick;
 
+class Checkpoint;
+
 void serializeAll(const std::string &cpt_dir);
-void unserializeAll(const std::string &cpt_dir);
+Checkpoint *getCheckpoint(const std::string &cpt_dir);
+void unserializeGlobals(Checkpoint *cp);
 
 bool want_warn, warn_verbose;
 bool want_info, info_verbose;

src/python/swig/pyobject.hh

@@ -52,8 +52,14 @@ serializeAll(const std::string &cpt_dir)
     Serializable::serializeAll(cpt_dir);
 }
 
-inline void
-unserializeAll(const std::string &cpt_dir)
+inline Checkpoint *
+getCheckpoint(const std::string &cpt_dir)
 {
-    Serializable::unserializeAll(cpt_dir);
+    return new Checkpoint(cpt_dir);
+}
+
+inline void
+unserializeGlobals(Checkpoint *cp)
+{
+    Serializable::unserializeGlobals(cp);
 }

src/python/swig/sim_object.i

@@ -51,6 +51,8 @@ class SimObject {
     };
 
     void init();
+    void loadState(Checkpoint *cp);
+    void initState();
     void regStats();
     void regFormulas();
     void resetStats();

src/sim/process.cc

@@ -100,8 +100,8 @@ template class AuxVector<uint32_t>;
 template class AuxVector<uint64_t>;
 
 Process::Process(ProcessParams * params)
-    : SimObject(params), system(params->system), checkpointRestored(false),
-    max_stack_size(params->max_stack_size)
+    : SimObject(params), system(params->system),
+      max_stack_size(params->max_stack_size)
 {
     string in = params->input;
     string out = params->output;
@@ -233,7 +233,7 @@ Process::findFreeContext()
 }
 
 void
-Process::startup()
+Process::initState()
 {
     if (contextIds.empty())
         fatal("Process %s is not associated with any HW contexts!\n", name());
@@ -537,9 +537,6 @@ Process::unserialize(Checkpoint *cp, const std::string &section)
     // find the param in the checkpoint if you wanted to, like set a default
     // but in this case we'll just stick with the instantianted value if not
     // found.   
-
-    checkpointRestored = true;
-
 }
 
 

src/sim/process.hh

@@ -79,8 +79,6 @@ class Process : public SimObject
     /// running on.
     System *system;
 
-    bool checkpointRestored;
-
     // thread contexts associated with this process
     std::vector<int> contextIds;
 
@@ -130,8 +128,7 @@ class Process : public SimObject
     // constructor
     Process(ProcessParams * params);
 
-    // post initialization startup
-    virtual void startup();
+    virtual void initState();
 
   protected:
     /// Memory object for initialization (image loading)

src/sim/serialize.cc

@@ -451,17 +451,6 @@ Serializable::serializeAll(const string &cpt_dir)
     SimObject::serializeAll(outstream);
 }
 
-void
-Serializable::unserializeAll(const string &cpt_dir)
-{
-    string dir = Checkpoint::setDir(cpt_dir);
-
-    DPRINTFR(Config, "Loading checkpoint dir '%s'\n", dir);
-    Checkpoint *cp = new Checkpoint(dir);
-    unserializeGlobals(cp);
-    SimObject::unserializeAll(cp);
-}
-
 void
 Serializable::unserializeGlobals(Checkpoint *cp)
 {
@@ -561,9 +550,9 @@ Checkpoint::dir()
 
 
 Checkpoint::Checkpoint(const string &cpt_dir)
-    : db(new IniFile), cptDir(cpt_dir)
+    : db(new IniFile), cptDir(setDir(cpt_dir))
 {
-    string filename = cpt_dir + "/" + Checkpoint::baseFilename;
+    string filename = cptDir + "/" + Checkpoint::baseFilename;
     if (!db->load(filename)) {
         fatal("Can't load checkpoint file '%s'\n", filename);
     }

src/sim/serialize.hh

@@ -141,7 +141,6 @@ class Serializable
     static int ckptMaxCount;
     static int ckptPrevCount;
     static void serializeAll(const std::string &cpt_dir);
-    static void unserializeAll(const std::string &cpt_dir);
     static void unserializeGlobals(Checkpoint *cp);
 };
 

src/sim/sim_object.cc

@@ -73,6 +73,18 @@ SimObject::init()
 {
 }
 
+void
+SimObject::loadState(Checkpoint *cp)
+{
+    if (cp->sectionExists(name()))
+        unserialize(cp, name());
+}
+
+void
+SimObject::initState()
+{
+}
+
 void
 SimObject::startup()
 {

src/sim/sim_object.hh

@@ -91,17 +91,48 @@ class SimObject : public EventManager, public Serializable
 
     virtual const std::string name() const { return params()->name; }
 
-    // initialization pass of all objects.
-    // Gets invoked after construction, before unserialize.
+    // The following SimObject initialization methods are called from
+    // the instantiate() method in src/python/m5/simulate.py.  See
+    // that function for details on how/when these methods are
+    // invoked.
+
+    /**
+     * init() is called after all C++ SimObjects have been created and
+     * all ports are connected.  Initializations that are independent
+     * of unserialization but rely on a fully instantiated and
+     * connected SimObject graph should be done here.
+     */
     virtual void init();
 
+    /**
+     * loadState() is called on each SimObject when restoring from a
+     * checkpoint.  The default implementation simply calls
+     * unserialize() if there is a corresponding section in the
+     * checkpoint.  However, objects can override loadState() to get
+     * other behaviors, e.g., doing other programmed initializations
+     * after unserialize(), or complaining if no checkpoint section is
+     * found.
+     */
+    virtual void loadState(Checkpoint *cp);
+
+    /**
+     * initState() is called on each SimObject when *not* restoring
+     * from a checkpoint.  This provides a hook for state
+     * initializations that are only required for a "cold start".
+     */
+    virtual void initState();
+
     // register statistics for this object
     virtual void regStats();
     virtual void regFormulas();
     virtual void resetStats();
 
-    // final initialization before simulation
-    // all state is unserialized so 
+    /**
+     * startup() is the final initialization call before simulation.
+     * All state is initialized (including unserialized state, if any,
+     * such as the curTick value), so this is the appropriate place to
+     * schedule initial event(s) for objects that need them.
+     */
     virtual void startup();
 
     // static: call nameOut() & serialize() on all SimObjects