ruby: mesi two,three level: copy data only when dirty

The level 2 controller has a bug. In one particular action, the data block was
copied from a message irrespective whether the block is dirty or not.  In cases
when L1 sends no data, the data value copied was incorrect.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/mem/protocol/MESI_Two_Level-L2cache.sm b/src/mem/protocol/MESI_Two_Level-L2cache.sm
index ede420626..6afd0fcea 100644
--- a/src/mem/protocol/MESI_Two_Level-L2cache.sm
+++ b/src/mem/protocol/MESI_Two_Level-L2cache.sm
@@ -628,8 +628,8 @@ machine(L2Cache, "MESI Directory L2 Cache CMP")
   action(mr_writeDataToCacheFromRequest, "mr", desc="Write data from response queue to cache") {
     peek(L1RequestL2Network_in, RequestMsg) {
       assert(is_valid(cache_entry));
-      cache_entry.DataBlk := in_msg.DataBlk;
       if (in_msg.Dirty) {
+        cache_entry.DataBlk := in_msg.DataBlk;
         cache_entry.Dirty := in_msg.Dirty;
       }
     }