# Copyright (c) 2021 The Regents of the University of California
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#
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# notice, this list of conditions and the following disclaimer;
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# neither the name of the copyright holders nor the names of its
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#
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"""

This script shows an example of running a full system Ubuntu boot simulation
using the gem5 library. This simulation boots Ubuntu 18.04 using 2 KVM CPU
cores. The simulation then switches to 2 Timing CPU cores before running an
echo statement.

Usage
-----

```
scons build/X86/gem5.opt
./build/X86/gem5.opt configs/example/gem5_library/x86-ubuntu-run-with-kvm.py
```
"""

from gem5.utils.requires import requires
from gem5.components.boards.x86_board import X86Board
from gem5.components.memory.single_channel import SingleChannelDDR3_1600
from gem5.components.processors.simple_switchable_processor import (
    SimpleSwitchableProcessor,
)
from gem5.components.processors.cpu_types import CPUTypes
from gem5.isas import ISA
from gem5.coherence_protocol import CoherenceProtocol
from gem5.resources.resource import Resource
from gem5.simulate.simulator import Simulator
from gem5.simulate.exit_event import ExitEvent

# This runs a check to ensure the gem5 binary is compiled to X86 and to the
# MESI Two Level coherence protocol.
requires(
    isa_required=ISA.X86,
    coherence_protocol_required=CoherenceProtocol.MESI_TWO_LEVEL,
    kvm_required=True,
)

from gem5.components.cachehierarchies.ruby.\
    mesi_two_level_cache_hierarchy import (
    MESITwoLevelCacheHierarchy,
)

# Here we setup a MESI Two Level Cache Hierarchy.
cache_hierarchy = MESITwoLevelCacheHierarchy(
    l1d_size="16kB",
    l1d_assoc=8,
    l1i_size="16kB",
    l1i_assoc=8,
    l2_size="256kB",
    l2_assoc=16,
    num_l2_banks=1,
)

# Setup the system memory.
memory = SingleChannelDDR3_1600(size="3GB")

# Here we setup the processor. This is a special switchable processor in which
# a starting core type and a switch core type must be specified. Once a
# configuration is instantiated a user may call `processor.switch()` to switch
# from the starting core types to the switch core types. In this simulation
# we start with KVM cores to simulate the OS boot, then switch to the Timing
# cores for the command we wish to run after boot.
processor = SimpleSwitchableProcessor(
    starting_core_type=CPUTypes.KVM,
    switch_core_type=CPUTypes.TIMING,
    num_cores=2,
)

# Here we setup the board. The X86Board allows for Full-System X86 simulations.
board = X86Board(
    clk_freq="3GHz",
    processor=processor,
    memory=memory,
    cache_hierarchy=cache_hierarchy,
)

# 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.

# This is the command to run after the system has booted. The first `m5 exit`
# will stop the simulation so we can switch the CPU cores from KVM to timing
# and continue the simulation to run the echo command, sleep for a second,
# then, again, call `m5 exit` to terminate the simulation. After simulation
# has ended you may inspect `m5out/system.pc.com_1.device` to see the echo
# output.
command = "m5 exit;" \
        + "echo 'This is running on Timing CPU cores.';" \
        + "sleep 1;" \
        + "m5 exit;"

board.set_kernel_disk_workload(
    # The x86 linux kernel will be automatically downloaded to the if not
    # already present.
    kernel=Resource("x86-linux-kernel-5.4.49"),
    # The x86 ubuntu image will be automatically downloaded to the if not
    # already present.
    disk_image=Resource("x86-ubuntu-img"),
    readfile_contents=command,
)

simulator = Simulator(
    board=board,
    on_exit_event={
        # Here we want override the default behavior for the first m5 exit
        # exit event. Instead of exiting the simulator, we just want to
        # switch the processor. The 2nd m5 exit after will revert to using
        # default behavior where the simulator run will exit.
        ExitEvent.EXIT : (func() for func in [processor.switch]),
    },
)
simulator.run()