kvm: Add checkpoint debug print

Add a debug print (when the Checkpoint debug flag is set) on serialize
and unserialize. Additionally, dump the KVM state before
serializing. The KVM state isn't dumped after unserializing since the
state is loaded lazily on the next KVM entry.

src/cpu/kvm/base.cc

@@ -48,6 +48,7 @@
 
 #include "arch/utility.hh"
 #include "cpu/kvm/base.hh"
+#include "debug/Checkpoint.hh"
 #include "debug/Kvm.hh"
 #include "debug/KvmIO.hh"
 #include "debug/KvmRun.hh"
@@ -213,6 +214,11 @@ BaseKvmCPU::regStats()
 void
 BaseKvmCPU::serializeThread(std::ostream &os, ThreadID tid)
 {
+    if (DTRACE(Checkpoint)) {
+        DPRINTF(Checkpoint, "KVM: Serializing thread %i:\n", tid);
+        dump();
+    }
+
     // Update the thread context so we have something to serialize.
     syncThreadContext();
 
@@ -225,6 +231,8 @@ void
 BaseKvmCPU::unserializeThread(Checkpoint *cp, const std::string &section,
                               ThreadID tid)
 {
+    DPRINTF(Checkpoint, "KVM: Unserialize thread %i:\n", tid);
+
     assert(tid == 0);
     assert(_status == Idle);
     thread->unserialize(cp, section);