Several more fixes for multi-level timing coherence.

- Add "deferred snoop" flag to Packet so upper-level caches
  can distinguish whether lower-level cache request was
  in-service or not at the time of the original snoop.
- Revamp response handling to properly handle deferred snoops
  on non-cache-fill requests (i.e. upgrades).
- Make sure forwarded writebacks are kept in write buffer at
  lower-level caches so they get snooped properly.

--HG--
extra : convert_revision : 17f8a3772a1ae31a16991a53f8225ddf54d31fc9

2 files changed, 10 insertions, 10 deletions

diff --git a/src/mem/cache/miss/mshr.cc b/src/mem/cache/miss/mshr.cc
index 5d5e63f90..7ba3789fe 100644
--- a/src/mem/cache/miss/mshr.cc
+++ b/src/mem/cache/miss/mshr.cc
@@ -119,25 +119,23 @@ MSHR::allocateTarget(PacketPtr target, Tick whenReady, Counter _order)
     ++ntargets;
 }
 
-void
-MSHR::allocateSnoopTarget(PacketPtr pkt, Tick whenReady, Counter _order)
+bool
+MSHR::handleSnoop(PacketPtr pkt, Counter _order)
 {
-    assert(inService); // don't bother to call otherwise
+    if (!inService || (pkt->isExpressSnoop() && !pkt->isDeferredSnoop())) {
+        return false;
+    }
 
     if (pendingInvalidate) {
         // a prior snoop has already appended an invalidation, so
         // logically we don't have the block anymore...
-        return;
+        return true;
     }
 
-    DPRINTF(Cache, "deferred snoop on %x: %s %s\n", addr,
-            needsExclusive ? "needsExclusive" : "",
-            pkt->needsExclusive() ? "pkt->needsExclusive()" : "");
-
     if (needsExclusive || pkt->needsExclusive()) {
         // actual target device (typ. PhysicalMemory) will delete the
         // packet on reception, so we need to save a copy here
-        targets.push_back(Target(new Packet(pkt), whenReady, _order, false));
+        targets.push_back(Target(new Packet(pkt), curTick, _order, false));
         ++ntargets;
 
         if (needsExclusive) {
@@ -157,6 +155,8 @@ MSHR::allocateSnoopTarget(PacketPtr pkt, Tick whenReady, Counter _order)
         pendingShared = true;
         pkt->assertShared();
     }
+
+    return true;
 }
 
 
diff --git a/src/mem/cache/miss/mshr.hh b/src/mem/cache/miss/mshr.hh
index a27f465aa..9c6a8cf33 100644
--- a/src/mem/cache/miss/mshr.hh
+++ b/src/mem/cache/miss/mshr.hh
@@ -162,7 +162,7 @@ public:
      * @param target The target.
      */
     void allocateTarget(PacketPtr target, Tick when, Counter order);
-    void allocateSnoopTarget(PacketPtr target, Tick when, Counter order);
+    bool handleSnoop(PacketPtr target, Counter order);
 
     /** A simple constructor. */
     MSHR();