mem: Added support for Null data packet

The packet now identifies whether static or dynamic data has been allocated and
is used by Ruby to determine whehter to copy the data pointer into the ruby
request.  Subsequently, Ruby can be told not to update phys memory when
receiving packets.

src/mem/packet.hh

@@ -681,9 +681,9 @@ class Packet : public FastAlloc, public Printable
      */
     template <typename T>
     T*
-    getPtr()
+    getPtr(bool null_ok = false)
     {
-        assert(flags.isSet(STATIC_DATA|DYNAMIC_DATA));
+        assert(null_ok || flags.isSet(STATIC_DATA|DYNAMIC_DATA));
         return (T*)data;
     }
 
@@ -768,7 +768,6 @@ class Packet : public FastAlloc, public Printable
         data = new uint8_t[getSize()];
     }
 
-
     /**
      * Check a functional request against a memory value represented
      * by a base/size pair and an associated data array.  If the

src/mem/ruby/system/DMASequencer.cc

@@ -97,8 +97,10 @@ DMASequencer::makeRequest(const RubyRequest &request)
     msg->getLen() = (offset + len) <= RubySystem::getBlockSizeBytes() ?
         len : RubySystem::getBlockSizeBytes() - offset;
 
-    if (write) {
-        msg->getDataBlk().setData(data, offset, msg->getLen());
+    if (write && (data != NULL)) {
+        if (active_request.data != NULL) {
+            msg->getDataBlk().setData(data, offset, msg->getLen());
+        }
     }
 
     assert(m_mandatory_q_ptr != NULL);
@@ -160,8 +162,10 @@ DMASequencer::dataCallback(const DataBlock & dblk)
     if (active_request.bytes_completed == 0)
         offset = active_request.start_paddr & m_data_block_mask;
     assert(active_request.write == false);
-    memcpy(&active_request.data[active_request.bytes_completed],
-           dblk.getData(offset, len), len);
+    if (active_request.data != NULL) {
+        memcpy(&active_request.data[active_request.bytes_completed],
+               dblk.getData(offset, len), len);
+    }
     issueNext();
 }
 

src/mem/ruby/system/RubyPort.cc

@@ -51,6 +51,7 @@ RubyPort::RubyPort(const Params *p)
     physMemPort = NULL;
 
     m_usingRubyTester = p->using_ruby_tester;
+    access_phys_mem = p->access_phys_mem;
 }
 
 void
@@ -64,7 +65,8 @@ Port *
 RubyPort::getPort(const std::string &if_name, int idx)
 {
     if (if_name == "port") {
-        return new M5Port(csprintf("%s-port%d", name(), idx), this);
+        return new M5Port(csprintf("%s-port%d", name(), idx), this,
+                          access_phys_mem);
     }
 
     if (if_name == "pio_port") {
@@ -80,7 +82,8 @@ RubyPort::getPort(const std::string &if_name, int idx)
         // RubyPort should only have one port to physical memory
         assert (physMemPort == NULL);
 
-        physMemPort = new M5Port(csprintf("%s-physMemPort", name()), this);
+        physMemPort = new M5Port(csprintf("%s-physMemPort", name()), this,
+                                 access_phys_mem);
 
         return physMemPort;
     }
@@ -105,12 +108,13 @@ RubyPort::PioPort::PioPort(const std::string &_name,
 }
 
 RubyPort::M5Port::M5Port(const std::string &_name,
-                         RubyPort *_port)
+                         RubyPort *_port, bool _access_phys_mem)
     : SimpleTimingPort(_name, _port)
 {
     DPRINTF(Ruby, "creating port from ruby sequcner to cpu %s\n", _name);
     ruby_port = _port;
     _onRetryList = false;
+    access_phys_mem = _access_phys_mem;
 }
 
 Tick
@@ -245,7 +249,7 @@ RubyPort::M5Port::recvTiming(PacketPtr pkt)
         }
     }
 
-    RubyRequest ruby_request(pkt->getAddr(), pkt->getPtr<uint8_t>(),
+    RubyRequest ruby_request(pkt->getAddr(), pkt->getPtr<uint8_t>(true),
                              pkt->getSize(), pc, type,
                              RubyAccessMode_Supervisor, pkt);
 
@@ -320,9 +324,10 @@ RubyPort::M5Port::hitCallback(PacketPtr pkt)
     bool needsResponse = pkt->needsResponse();
 
     //
-    // All responses except failed SC operations access M5 physical memory
+    // Unless specified at configuraiton, all responses except failed SC 
+    // operations access M5 physical memory.
     //
-    bool accessPhysMem = true;
+    bool accessPhysMem = access_phys_mem;
 
     if (pkt->isLLSC()) {
         if (pkt->isWrite()) {
@@ -351,13 +356,12 @@ RubyPort::M5Port::hitCallback(PacketPtr pkt)
 
     if (accessPhysMem) {
         ruby_port->physMemPort->sendAtomic(pkt);
+    } else {
+        pkt->makeResponse();
     }
 
     // turn packet around to go back to requester if response expected
     if (needsResponse) {
-        // sendAtomic() should already have turned packet into
-        // atomic response
-        assert(pkt->isResponse());
         DPRINTF(MemoryAccess, "Sending packet back over port\n");
         sendTiming(pkt);
     } else {

src/mem/ruby/system/RubyPort.hh

@@ -51,9 +51,11 @@ class RubyPort : public MemObject
       private:
         RubyPort *ruby_port;
         bool _onRetryList;
+        bool access_phys_mem;
 
       public:
-        M5Port(const std::string &_name, RubyPort *_port);
+        M5Port(const std::string &_name, RubyPort *_port,
+               bool _access_phys_mem);
         bool sendTiming(PacketPtr pkt);
         void hitCallback(PacketPtr pkt);
         unsigned deviceBlockSize() const;
@@ -151,6 +153,7 @@ class RubyPort : public MemObject
     std::list<M5Port*> retryList;
 
     bool waitingOnSequencer;
+    bool access_phys_mem;
 };
 
 #endif // __MEM_RUBY_SYSTEM_RUBYPORT_HH__

src/mem/ruby/system/Sequencer.py

@@ -40,7 +40,9 @@ class RubyPort(MemObject):
     physmem = Param.PhysicalMemory("")
     physMemPort = Port("port to physical memory")
     using_ruby_tester = Param.Bool(False, "")
-
+    access_phys_mem = Param.Bool(True,
+        "should the rubyport atomically update phys_mem")
+    
 class RubySequencer(RubyPort):
     type = 'RubySequencer'
     cxx_class = 'Sequencer'