mem: Filter cache snoops based on address ranges

This patch adds a filter to the cache to drop snoop requests that are
not for a range covered by the cache. This fixes an issue observed
when multiple caches are placed in parallel, covering different
address ranges. Without this patch, all the caches will forward the
snoop upwards, when only one should do so.

diff --git a/src/mem/cache/cache_impl.hh b/src/mem/cache/cache_impl.hh
index 76fb697c25b40d124410966ac6f6b95c25fe47e4..b482d6314628d4998ade331d7ef47d86dcc778f6 100644 (file)
--- a/src/mem/cache/cache_impl.hh
+++ b/src/mem/cache/cache_impl.hh
@@ -1475,10 +1475,23 @@ Cache<TagStore>::recvTimingSnoopReq(PacketPtr pkt)
     // Snoops shouldn't happen when bypassing caches
     assert(!system->bypassCaches());
 
+    // check if the packet is for an address range covered by this
+    // cache, partly to not waste time looking for it, but also to
+    // ensure that we only forward the snoop upwards if it is within
+    // our address ranges
+    bool in_range = false;
+    for (AddrRangeList::const_iterator r = addrRanges.begin();
+         r != addrRanges.end(); ++r) {
+        if (r->contains(pkt->getAddr())) {
+            in_range = true;
+            break;
+        }
+    }
+
     // Note that some deferred snoops don't have requests, since the
     // original access may have already completed
     if ((pkt->req && pkt->req->isUncacheable()) ||
-        pkt->cmd == MemCmd::Writeback) {
+        pkt->cmd == MemCmd::Writeback || !in_range) {
         //Can't get a hit on an uncacheable address
         //Revisit this for multi level coherence
         return;