mem: write streaming support via WriteInvalidate promotion

Support full-block writes directly rather than requiring RMW:
 * a cache line is allocated in the cache upon receipt of a
   WriteInvalidateReq, not the WriteInvalidateResp.
 * only top-level caches allocate the line; the others just pass
   the request along and invalidate as necessary.
 * to close a timing window between the *Req and the *Resp, a new
   metadata bit tracks whether another cache has read a copy of
   the new line before the writeback to memory.

1 files changed, 3 insertions, 0 deletions

diff --git a/src/mem/cache/base.hh b/src/mem/cache/base.hh
index 1567aaa62..297b80180 100644
--- a/src/mem/cache/base.hh
+++ b/src/mem/cache/base.hh
@@ -94,6 +94,7 @@ class BaseCache : public MemObject
         Blocked_NoMSHRs = MSHRQueue_MSHRs,
         Blocked_NoWBBuffers = MSHRQueue_WriteBuffer,
         Blocked_NoTargets,
+        Blocked_PendingWriteInvalidate,
         NUM_BLOCKED_CAUSES
     };
 
@@ -168,6 +169,8 @@ class BaseCache : public MemObject
         /** Return to normal operation and accept new requests. */
         void clearBlocked();
 
+        bool isBlocked() const { return blocked; }
+
       protected:
 
         CacheSlavePort(const std::string &_name, BaseCache *_cache,