config,arch,cpu,kern,sim: Extract kernel information from System.

Information about what kernel to load and how to load it was built
into the System object and its subclasses. That overloaded the System
object and made it responsible for too many things, and also was
somewhat awkward when working with SE mode which doesn't have a kernel.

This change extracts the kernel and information related to it from the
System object and puts into into a OsKernel or Workload object.
Currently the idea of a "Workload" to run and a kernel are a bit
muddled, an unfortunate carry-over from the original code. It's also an
implication of trying not to make too sweeping of a change, and to
minimize the number of times configs need to change, ie avoiding
creating a "kernel" parameter which would shortly thereafter be
renamed to "workload".

In future changes, the ideas of a kernel and a workload will be
disentangled, and workloads will be expanded to include emulated
operating systems which shephard and contain Process-es for syscall
emulation.

This change was originally split into pieces to make reviewing it
easier. Those reviews are here:

https: //gem5-review.googlesource.com/c/public/gem5/+/22243
https: //gem5-review.googlesource.com/c/public/gem5/+/24144
https: //gem5-review.googlesource.com/c/public/gem5/+/24145
https: //gem5-review.googlesource.com/c/public/gem5/+/24146
https: //gem5-review.googlesource.com/c/public/gem5/+/24147
https: //gem5-review.googlesource.com/c/public/gem5/+/24286

Change-Id: Ia3d863db276a023b6a2c7ee7a656d8142ff75589
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/26466
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>
Tested-by: kokoro <noreply+kokoro@google.com>

src/arch/arm/ArmSystem.py

@@ -41,23 +41,12 @@ from m5.util.fdthelper import *
 from m5.objects.System import System
 from m5.objects.ArmSemihosting import ArmSemihosting
 
-class ArmMachineType(Enum):
-    map = {
-        'VExpress_EMM' : 2272,
-        'VExpress_EMM64' : 2272,
-        'DTOnly' : -1,
-    }
-
 class SveVectorLength(UInt8): min = 1; max = 16
 
 class ArmSystem(System):
     type = 'ArmSystem'
     cxx_header = "arch/arm/system.hh"
     multi_proc = Param.Bool(True, "Multiprocessor system?")
-    boot_loader = VectorParam.String([],
-        "File that contains the boot loader code. Zero or more files may be "
-        "specified. The first boot loader that matches the kernel's "
-        "architecture will be used.")
     gic_cpu_addr = Param.Addr(0, "Addres of the GIC CPU interface")
     flags_addr = Param.Addr(0, "Address of the flags register for MP booting")
     have_security = Param.Bool(False,
@@ -90,10 +79,11 @@ class ArmSystem(System):
     semihosting = Param.ArmSemihosting(NULL,
         "Enable support for the Arm semihosting by settings this parameter")
 
-    dtb_filename = Param.String("",
-        "File that contains the Device Tree Blob. Don't use DTB if empty.")
+    m5ops_base = Param.Addr(0,
+        "Base of the 64KiB PA range used for memory-mapped m5ops. Set to 0 "
+        "to disable.")
 
-    def generateDtb(self, outdir, filename):
+    def generateDtb(self, filename):
         """
         Autogenerate DTB. Arguments are the folder where the DTB
         will be stored, and the name of the DTB file.
@@ -103,8 +93,7 @@ class ArmSystem(System):
 
         fdt = Fdt()
         fdt.add_rootnode(rootNode)
-        dtb_filename = os.path.join(outdir, filename)
-        self.dtb_filename = fdt.writeDtbFile(dtb_filename)
+        fdt.writeDtbFile(filename)
 
 
     def generateDeviceTree(self, state):
@@ -139,37 +128,3 @@ class ArmSystem(System):
                 root.append(node)
 
         return root
-
-class GenericArmSystem(ArmSystem):
-    type = 'GenericArmSystem'
-    cxx_header = "arch/arm/system.hh"
-    machine_type = Param.ArmMachineType('DTOnly',
-        "Machine id from http://www.arm.linux.org.uk/developer/machines/")
-    atags_addr = Param.Addr("Address where default atags structure should " \
-                                "be written")
-    early_kernel_symbols = Param.Bool(False,
-        "enable early kernel symbol tables before MMU")
-    enable_context_switch_stats_dump = Param.Bool(False,
-        "enable stats/task info dumping at context switch boundaries")
-
-    panic_on_panic = Param.Bool(False, "Trigger a gem5 panic if the " \
-                                    "guest kernel panics")
-    panic_on_oops = Param.Bool(False, "Trigger a gem5 panic if the " \
-                                   "guest kernel oopses")
-
-class LinuxArmSystem(GenericArmSystem):
-    type = 'LinuxArmSystem'
-    cxx_header = "arch/arm/linux/system.hh"
-
-    @cxxMethod
-    def dumpDmesg(self):
-        """Dump dmesg from the simulated kernel to standard out"""
-        pass
-
-    # Have Linux systems for ARM auto-calc their load_addr_mask for proper
-    # kernel relocation.
-    load_addr_mask = 0x0
-
-class FreebsdArmSystem(GenericArmSystem):
-    type = 'FreebsdArmSystem'
-    cxx_header = "arch/arm/freebsd/system.hh"