stdlib: Extend AbstractBoard pre_instantiation functionality (#1497)

* Deprecates the setting of FS/SE mode via the `Simulator` module.
* Moved the creation of the `Root` object from the `Simulator` to the
board.
* Moved the setting of `sim_quantum` from the `Simulator` to the
processor.
* Allows for easier development of boards which support both SE and FS
mode simulation by moving board setup function calls to occur after the
set_workload function is call which sets a boards stats `is_fs` status.

tests/gem5/kvm_fork_tests/configs/boot_kvm_fork_run.py

@@ -207,15 +207,15 @@ print("Running with ISA: " + processor.get_isa().name)
 print("Running with protocol: " + get_runtime_coherence_protocol().name)
 print()
 
-root = Root(full_system=True, system=motherboard)
+# Disable the gdb ports. Required for forking.
+m5.disableAllListeners()
+root = motherboard._pre_instantiate()
 
 # TODO: This of annoying. Is there a way to fix this to happen
 # automatically when running KVM?
 root.sim_quantum = int(1e9)
 
-# Disable the gdb ports. Required for forking.
-m5.disableAllListeners()
-motherboard._pre_instantiate()
+
 m5.instantiate()
 
 # Simulate the inital boot with the starting KVM cpu

tests/gem5/replacement_policies/configs/run_replacement_policy.py

@@ -83,9 +83,8 @@ motherboard = TestBoard(
     memory=memory,
     cache_hierarchy=cache_hierarchy,
 )
-root = Root(full_system=False, system=motherboard)
 
-motherboard._pre_instantiate()
+root = motherboard._pre_instantiate()
 m5.instantiate()
 
 generator.start_traffic()

tests/gem5/replacement_policies/run_replacement_policy.py

@@ -83,9 +83,8 @@ motherboard = TestBoard(
     memory=memory,
     cache_hierarchy=cache_hierarchy,
 )
-root = Root(full_system=False, system=motherboard)
 
-motherboard._pre_instantiate()
+root = motherboard._pre_instantiate()
 m5.instantiate()
 
 generator.start_traffic()

tests/gem5/traffic_gen/configs/simple_traffic_run.py

@@ -202,9 +202,7 @@ motherboard = TestBoard(
     cache_hierarchy=cache_hierarchy,
 )
 
-root = Root(full_system=False, system=motherboard)
-
-motherboard._pre_instantiate()
+root = motherboard._pre_instantiate()
 m5.instantiate()
 
 generator.start_traffic()