stdlib: Fix SwitchableProcessor use in SE mode

The SwitchableProcessors in the standard library have switched-in and
switched-out cores. The `get_cores` API in the stdlib only returns
switched-in cores. In most uses this is desirable.

In the case of setting workloads in SE mode it's necessary to set the
workload to every core, switched-in and switched-out. As the `get_cores`
function was used for this, SwitchableProcessors were failing when used
in SE Mode.

This patch checks the processor type and, if a SwitchableProcessor, uses
the SwitchableProcessor's special `_all_cores` function which gets all
the cores, regardless as to their switched-in/switched-out status.

Issue-on: https://gem5.atlassian.net/browse/GEM5-1320

Change-Id: I0b7a699ac6196e827667955bef7afa37b2648744
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/68997
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Maintainer: Bobby Bruce <bbruce@ucdavis.edu>
Reviewed-by: Bobby Bruce <bbruce@ucdavis.edu>

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

@@ -35,6 +35,8 @@ from ...resources.resource import (
     SimpointDirectoryResource,
 )
 
+from ..processors.switchable_processor import SwitchableProcessor
+
 from gem5.resources.elfie import ELFieInfo
 from gem5.resources.looppoint import Looppoint
 
@@ -112,8 +114,23 @@ class SEBinaryWorkload:
         if env_list is not None:
             process.env = env_list
 
-        for core in self.get_processor().get_cores():
-            core.set_workload(process)
+        if isinstance(self.get_processor(), SwitchableProcessor):
+            # This is a hack to get switchable processors working correctly in
+            # SE mode. The "get_cores" API for processors only gets the current
+            # switched-in cores and, in most cases, this is what the script
+            # required. In the case there are switched-out cores via the
+            # SwitchableProcessor, we sometimes need to apply things to ALL
+            # cores (switched-in or switched-out). In this case we have an
+            # `__all_cores` function. Here we must apply the process to every
+            # core.
+            #
+            # A better API for this which avoids `isinstance` checks would be
+            # welcome.
+            for core in self.get_processor()._all_cores():
+                core.set_workload(process)
+        else:
+            for core in self.get_processor().get_cores():
+                core.set_workload(process)
 
         # Set whether to exit on work items for the se_workload
         self.exit_on_work_items = exit_on_work_items