stdlib: Fix SimpleSwitchableProcessor to allow Minor type

Without setting the correct memory mode the SimpleSwitchableProcessor,
the Minor CPU could not be used as a valid core. This patch corrects
this issue by setting the memory mode to TIMING for Minor CPU cores.

Due to the increasingly complex if-else to determine the memory mode, a
function has been added to CPUTypes to determine what MemMode is
required for each CPUType.

Change-Id: I9384b4a9c0673af34cca04917d763ca45d0ea434
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/61535
Tested-by: kokoro <noreply+kokoro@google.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>

src/python/gem5/components/processors/cpu_types.py

@@ -24,6 +24,8 @@
 # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
+from ..boards.mem_mode import MemMode
+
 from enum import Enum
 from typing import Set
 import os
@@ -68,3 +70,21 @@ def get_cpu_type_from_str(input: str) -> CPUTypes:
         f"CPU type '{input}' does not correspond to a known CPU type. "
         f"Known CPU Types:{valid_cpu_types_list_str}"
     )
+
+
+def get_mem_mode(input: CPUTypes) -> MemMode:
+    """
+    Returns the correct memory mode to be set for a given CPUType.
+
+    :param input: The CPUType to check.
+    """
+
+    cpu_mem_mode_map = {
+        CPUTypes.TIMING: MemMode.TIMING,
+        CPUTypes.O3: MemMode.TIMING,
+        CPUTypes.MINOR: MemMode.TIMING,
+        CPUTypes.KVM: MemMode.ATOMIC_NONCACHING,
+        CPUTypes.ATOMIC: MemMode.ATOMIC,
+    }
+
+    return cpu_mem_mode_map[input]

src/python/gem5/components/processors/simple_switchable_processor.py

@@ -27,7 +27,7 @@
 from ..boards.mem_mode import MemMode
 from ..boards.abstract_board import AbstractBoard
 from ..processors.simple_core import SimpleCore
-from ..processors.cpu_types import CPUTypes
+from ..processors.cpu_types import CPUTypes, get_mem_mode
 from .switchable_processor import SwitchableProcessor
 from ...isas import ISA
 
@@ -72,14 +72,7 @@ class SimpleSwitchableProcessor(SwitchableProcessor):
         self._switch_key = "switch"
         self._current_is_start = True
 
-        if starting_core_type in (CPUTypes.TIMING, CPUTypes.O3):
-            self._mem_mode = MemMode.TIMING
-        elif starting_core_type == CPUTypes.KVM:
-            self._mem_mode = MemMode.ATOMIC_NONCACHING
-        elif starting_core_type == CPUTypes.ATOMIC:
-            self._mem_mode = MemMode.ATOMIC
-        else:
-            raise NotImplementedError
+        self._mem_mode = get_mem_mode(starting_core_type)
 
         switchable_cores = {
             self._start_key: [