mem: use default backdoor behavior for thread_bridge

The original backdoor implementation is incorrect. We use simply
fallback to default (disable backdoor) as backdoor across threads is not
thread-safe in most of cases.

Change-Id: Ia39be0dda4f16917cc3565eb5b012270e6d7697a
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/67531
Maintainer: Gabe Black <gabe.black@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Yu-hsin Wang <yuhsingw@google.com>

src/mem/thread_bridge.cc

@@ -64,12 +64,6 @@ ThreadBridge::IncomingPort::recvRespRetry()
 
 // AtomicResponseProtocol
 Tick
-ThreadBridge::IncomingPort::recvAtomicBackdoor(PacketPtr pkt,
-                                               MemBackdoorPtr &backdoor)
-{
-    panic("ThreadBridge only supports atomic/functional access.");
-}
-Tick
 ThreadBridge::IncomingPort::recvAtomic(PacketPtr pkt)
 {
     EventQueue::ScopedMigration migrate(device_.eventQueue());
@@ -84,14 +78,6 @@ ThreadBridge::IncomingPort::recvFunctional(PacketPtr pkt)
     device_.out_port_.sendFunctional(pkt);
 }
 
-void
-ThreadBridge::IncomingPort::recvMemBackdoorReq(const MemBackdoorReq &req,
-                                               MemBackdoorPtr &backdoor)
-{
-    EventQueue::ScopedMigration migrate(device_.eventQueue());
-    device_.out_port_.sendMemBackdoorReq(req, backdoor);
-}
-
 ThreadBridge::OutgoingPort::OutgoingPort(const std::string &name,
                                          ThreadBridge &device)
     : RequestPort(name), device_(device)

src/mem/thread_bridge.hh

@@ -55,14 +55,10 @@ class ThreadBridge : public SimObject
         void recvRespRetry() override;
 
         // AtomicResponseProtocol
-        Tick recvAtomicBackdoor(PacketPtr pkt,
-                                MemBackdoorPtr &backdoor) override;
         Tick recvAtomic(PacketPtr pkt) override;
 
         // FunctionalResponseProtocol
         void recvFunctional(PacketPtr pkt) override;
-        void recvMemBackdoorReq(const MemBackdoorReq &req,
-                                MemBackdoorPtr &backdoor) override;
 
       private:
         ThreadBridge &device_;