mem: Add support for writing back and flushing caches

This patch adds support for the following optional drain methods in
the classical memory system's cache model:

memWriteback() - Write back all dirty cache lines to memory using
functional accesses.

memInvalidate() - Invalidate all cache lines. Dirty cache lines
are lost unless a writeback is requested.

Since memWriteback() is called when checkpointing systems, this patch
adds support for checkpointing systems with caches. The serialization
code now checks whether there are any dirty lines in the cache. If
there are dirty lines in the cache, the checkpoint is flagged as bad
and a warning is printed.

1 files changed, 34 insertions, 1 deletions

diff --git a/src/mem/cache/mshr_queue.cc b/src/mem/cache/mshr_queue.cc
index b412891d9..af13d12d3 100644
--- a/src/mem/cache/mshr_queue.cc
+++ b/src/mem/cache/mshr_queue.cc
@@ -1,4 +1,16 @@
 /*
+ * Copyright (c) 2012 ARM Limited
+ * All rights reserved.
+ *
+ * The license below extends only to copyright in the software and shall
+ * not be construed as granting a license to any other intellectual
+ * property including but not limited to intellectual property relating
+ * to a hardware implementation of the functionality of the software
+ * licensed hereunder.  You may use the software subject to the license
+ * terms below provided that you ensure that this notice is replicated
+ * unmodified and in its entirety in all distributions of the software,
+ * modified or unmodified, in source code or in binary form.
+ *
  * Copyright (c) 2003-2005 The Regents of The University of Michigan
  * All rights reserved.
  *
@@ -26,6 +38,7 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *
  * Authors: Erik Hallnor
+ *          Andreas Sandberg
  */
 
 /** @file
@@ -40,7 +53,7 @@ MSHRQueue::MSHRQueue(const std::string &_label,
                      int num_entries, int reserve, int _index)
     : label(_label),
       numEntries(num_entries + reserve - 1), numReserve(reserve),
-      index(_index)
+      drainManager(NULL), index(_index)
 {
     allocated = 0;
     inServiceEntries = 0;
@@ -183,6 +196,13 @@ MSHRQueue::deallocateOne(MSHR *mshr)
         readyList.erase(mshr->readyIter);
     }
     mshr->deallocate();
+    if (drainManager && allocated == 0) {
+        // Notify the drain manager that we have completed draining if
+        // there are no other outstanding requests in this MSHR queue.
+        drainManager->signalDrainDone();
+        drainManager = NULL;
+        setDrainState(Drainable::Drained);
+    }
     return retval;
 }
 
@@ -245,3 +265,16 @@ MSHRQueue::squash(int threadNum)
         }
     }
 }
+
+unsigned int
+MSHRQueue::drain(DrainManager *dm)
+{
+    if (allocated == 0) {
+        setDrainState(Drainable::Drained);
+        return 0;
+    } else {
+        drainManager = dm;
+        setDrainState(Drainable::Draining);
+        return 1;
+    }
+}