stdlib: Move 'connect_things' to AbstractBoard constructor

This patch moves 'connect_things' to the AbstractBoard constructor,
thereby meaning it does not need to be called directly in gem5
configuration scripts. This method has been changed to private as a
result.

As boards that inherit from AbstractBoard require certain things to be
setup prior to `connect_things` being called, a new abstract function,
`_setup_board` has been created. This is called in the AbstractBoard
constructor before `connect_things` and can be overridden by boards to
setup board properties as required.

Change-Id: I558a4321b850a6b19e20b7d56d0bcae5805114b6
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/52184
Reviewed-by: Bobby R. Bruce <bbruce@ucdavis.edu>
Maintainer: Bobby R. Bruce <bbruce@ucdavis.edu>
Tested-by: kokoro <noreply+kokoro@google.com>

configs/example/gem5_library/arm-hello.py

@@ -75,10 +75,6 @@ board = SimpleBoard(
     cache_hierarchy=cache_hierarchy,
 )
 
-# This method must be called to connect all the components specified during
-# the board's construction.
-board.connect_things()
-
 # Here we set the workload. In this case we want to run a simple "Hello World!"
 # program compiled to the ARM ISA. The `Resource` class will automatically
 # download the binary from the gem5 Resources cloud bucket if it's not already

configs/example/gem5_library/riscv-fs.py

@@ -78,8 +78,6 @@ board = RiscvBoard(
     cache_hierarchy=cache_hierarchy,
 )
 
-board.connect_things()
-
 # Set the Full System workload.
 board.set_kernel_disk_workload(
                    kernel=Resource("riscv-bootloader-vmlinux-5.10"),

configs/example/gem5_library/x86-ubuntu-run.py

@@ -102,8 +102,6 @@ board = X86Board(
     cache_hierarchy=cache_hierarchy,
 )
 
-board.connect_things()
-
 # Here we set the Full System workload.
 # The `set_kernel_disk_workload` function for the X86Board takes a kernel, a
 # disk image, and, optionally, a command to run.

src/python/gem5/components/boards/abstract_board.py

@@ -92,7 +92,12 @@ class AbstractBoard(System):
         self.memory = memory
         self.cache_hierarchy = cache_hierarchy
 
-        self.setup_memory_ranges()
+
+        # Setup board properties unique to the board being constructed.
+        self._setup_board()
+
+        # Connect the memory, processor, and cache hierarchy.
+        self._connect_things()
 
     def get_processor(self) -> "AbstractProcessor":
         """Get the processor connected to the board.
@@ -135,11 +140,20 @@ class AbstractBoard(System):
 
     def get_clock_domain(self) -> ClockDomain:
         """Get the clock domain.
-
         :returns: The clock domain.
         """
         return self.clk_domain
 
+    @abstractmethod
+    def _setup_board(self) -> None:
+        """
+        This function is called in the AbstractBoard constructor, before the
+        memory, processor, and cache hierarchy components are incorporated via
+        `_connect_thing()`. This function should be overridden by boards to
+        specify components, connections unique to that board.
+        """
+        raise NotImplementedError
+
     # Technically `get_dma_ports` returns a list. This list could be empty to
     # indicate the presense of dma ports. Though I quite like having this
     # boolean to quickly check a board.
@@ -220,7 +234,7 @@ class AbstractBoard(System):
         raise NotImplementedError
 
     @final
-    def connect_things(self) -> None:
+    def _connect_things(self) -> None:
         """Connects all the components to the board.
 
         The order of this board is always:

src/python/gem5/components/boards/riscv_board.py

@@ -90,9 +90,10 @@ class RiscvBoard(AbstractBoard, KernelDiskWorkload):
         super().__init__(
             clk_freq, processor, memory, cache_hierarchy, exit_on_work_items
         )
-
         requires(isa_required=ISA.RISCV)
 
+    @overrides(AbstractBoard)
+    def _setup_board(self) -> None:
         self.workload = RiscvLinux()
 
         # Contains a CLINT, PLIC, UART, and some functions for the dtb, etc.

src/python/gem5/components/boards/simple_board.py

@@ -72,6 +72,8 @@ class SimpleBoard(AbstractBoard):
             exit_on_work_items=exit_on_work_items,
         )
 
+    @overrides(AbstractBoard)
+    def _setup_board(self) -> None:
         # Set up the memory ranges
         self.setup_memory_ranges()
 

src/python/gem5/components/boards/test_board.py

@@ -66,6 +66,8 @@ class TestBoard(AbstractBoard):
             cache_hierarchy=cache_hierarchy,
         )
 
+    @overrides(AbstractBoard)
+    def _setup_board(self) -> None:
         self.setup_memory_ranges()
 
     @overrides(AbstractBoard)

src/python/gem5/components/boards/x86_board.py

@@ -90,6 +90,8 @@ class X86Board(AbstractBoard, KernelDiskWorkload):
 
         requires(isa_required=ISA.X86)
 
+    @overrides(AbstractBoard)
+    def _setup_board(self) -> None:
         self.pc = Pc()
 
         self.workload = X86FsLinux()

tests/gem5/configs/boot_kvm_fork_run.py

@@ -195,8 +195,6 @@ motherboard = X86Board(
     exit_on_work_items=True,
 )
 
-motherboard.connect_things()
-
 # Set the Full System workload.
 motherboard.set_kernel_disk_workload(
     kernel=Resource(

tests/gem5/configs/boot_kvm_switch_exit.py

@@ -178,8 +178,6 @@ motherboard = X86Board(
     exit_on_work_items=True,
 )
 
-motherboard.connect_things()
-
 kernal_args = motherboard.get_default_kernel_args() + [args.kernel_args]
 
 # Set the Full System workload.

tests/gem5/configs/parsec_disk_run.py

@@ -214,8 +214,6 @@ board = X86Board(
     exit_on_work_items=True,
 )
 
-board.connect_things()
-
 # The command to run.
 command = (
     "cd /home/gem5/parsec-benchmark\n"

tests/gem5/configs/riscv_boot_exit_run.py

@@ -143,8 +143,6 @@ board = RiscvBoard(
     cache_hierarchy=cache_hierarchy,
 )
 
-board.connect_things()
-
 # Set the Full System workload.
 board.set_kernel_disk_workload(
     kernel=Resource(

tests/gem5/configs/simple_binary_run.py

@@ -93,8 +93,6 @@ motherboard = SimpleBoard(
     cache_hierarchy=cache_hierarchy,
 )
 
-motherboard.connect_things()
-
 # Set the workload
 binary = Resource(args.resource,
         resource_directory=args.resource_directory)

tests/gem5/configs/simple_traffic_run.py

@@ -131,8 +131,6 @@ motherboard = TestBoard(
     cache_hierarchy=cache_hierarchy,
 )
 
-motherboard.connect_things()
-
 root = Root(full_system=False, system=motherboard)
 
 m5.instantiate()

tests/gem5/configs/x86_boot_exit_run.py

@@ -185,8 +185,6 @@ motherboard = X86Board(
     exit_on_work_items=True,
 )
 
-motherboard.connect_things()
-
 kernal_args = motherboard.get_default_kernel_args()
 if args.boot_type == "init":
     kernal_args.append("init=/root/exit.sh")