configs: Allow for second disk in GPUFS

Connect the --second-disk option in GPUFS. Typically this is used as a
benchmarks disk image. If the disk is unmounted at the time of
checkpoint, a new disk image can be mounted after restoring the
checkpoint for a simple way to add new benchmarks without recreating a
checkpoint.

Change-Id: I57b31bdf8ec628006d774feacff3fde6f533cd4b
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/53071
Reviewed-by: Matt Sinclair <mattdsinclair@gmail.com>
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Matt Sinclair <mattdsinclair@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>

configs/example/gpufs/system/system.py

@@ -54,7 +54,10 @@ def makeGpuFSSystem(args):
 
     # Use the common FSConfig to setup a Linux X86 System
     (TestCPUClass, test_mem_mode, FutureClass) = Simulation.setCPUClass(args)
-    bm = SysConfig(disks=[args.disk_image], mem=args.mem_size)
+    disks = [args.disk_image]
+    if args.second_disk is not None:
+        disks.extend([args.second_disk])
+    bm = SysConfig(disks=disks, mem=args.mem_size)
     system = makeLinuxX86System(test_mem_mode, args.num_cpus, bm, True,
                                   cmdline=cmdline)
     system.workload.object_file = binary(args.kernel)