mem: Add support for CMOs in the cache

This change adds support for maintenance operations (CMOs) in the
cache. The supported memory operations clean and/or invalidate a cache
block as specified by its VA to the specified xbar (PoU, PoC).

A cache maintenance packet visits all memories down to the specified
xbar. Caches need to invalidate their copy if it is an invalidating
CMO. If it is (additionally) a cleaning CMO and a dirty copy exists,
the cache cleans it with a WriteClean request.

Change-Id: Ibf31daa7213925898f3408738b11b1dd76c90b79
Reviewed-by: Stephan Diestelhorst <stephan.diestelhorst@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/5049
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>

1 files changed, 19 insertions, 1 deletions

diff --git a/src/mem/packet.hh b/src/mem/packet.hh
index fcdd73a03..88829d358 100644
--- a/src/mem/packet.hh
+++ b/src/mem/packet.hh
@@ -42,6 +42,7 @@
  *          Steve Reinhardt
  *          Ali Saidi
  *          Andreas Hansson
+ *          Nikos Nikoleris
  */
 
 /**
@@ -259,7 +260,7 @@ class Packet : public Printable
 
     enum : FlagsType {
         // Flags to transfer across when copying a packet
-        COPY_FLAGS             = 0x0000001F,
+        COPY_FLAGS             = 0x0000003F,
 
         // Does this packet have sharers (which means it should not be
         // considered writable) or not. See setHasSharers below.
@@ -282,6 +283,10 @@ class Packet : public Printable
         // downstream by the receiver
         WRITE_THROUGH          = 0x00000010,
 
+        // Response co-ordination flag for cache maintenance
+        // operations
+        SATISFIED              = 0x00000020,
+
         /// Are the 'addr' and 'size' fields valid?
         VALID_ADDR             = 0x00000100,
         VALID_SIZE             = 0x00000200,
@@ -643,6 +648,19 @@ class Packet : public Printable
     void clearWriteThrough() { flags.clear(WRITE_THROUGH); }
     bool writeThrough() const { return flags.isSet(WRITE_THROUGH); }
 
+    /**
+     * Set when a request hits in a cache and the cache is not going
+     * to respond. This is used by the crossbar to coordinate
+     * responses for cache maintenance operations.
+     */
+    void setSatisfied()
+    {
+        assert(cmd.isClean());
+        assert(!flags.isSet(SATISFIED));
+        flags.set(SATISFIED);
+    }
+    bool satisfied() const { return flags.isSet(SATISFIED); }
+
     void setSuppressFuncError()     { flags.set(SUPPRESS_FUNC_ERROR); }
     bool suppressFuncError() const  { return flags.isSet(SUPPRESS_FUNC_ERROR); }
     void setBlockCached()          { flags.set(BLOCK_CACHED); }