OpenRISC 1000 Multicore Virtual Platform (or1kmvp)

This repository contains the source code of or1kmvp, an OpenRISC 1000 Multicore Virtual Platform based on SystemC/TLM. It models a regular symmetric multiprocessor design with a configurable number of processors and a set of I/O peripherals. or1kmvp is detailed enough to run the Linux kernel and fast enough to allow interactive command-line use. Depending on the host computer, this full system simulator reaches a total performance of around 35 MIPS (which are split among all instruction set simulators present in the system). It is intended to be used by software developers to test and run parallel OpenRISC applications without the need for physical OpenRISC hardware. Furthermore, it can also be used as a starting point for custom SystemC and OpenRISC based Virtual Platforms.

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Build & Installation

In order to build or1kmvp, you need the following prerequisite software libraries:

  • SystemC: the underlying simulation engine
  • or1kiss: the OpenRISC 1000 instruction set simulator
  • vcml: a SystemC addon library with TLM models for peripherals etc.
  • libelf: for reading ELF binaries
  • cmake: is used as the build system

These libraries should have guides on how to build them that take precedence over this one. However, for convenience, this is the full build procedure:

  1. Install libelf and cmake:

    sudo apt-get install cmake libelf-dev  # Ubuntu
    sudo yum install cmake3 libelf-dev     # Centos
    
  2. Download and build SystemC. Make sure to set the environment variables SYSTEMC_HOME and TARGET_ARCH afterwards:

    wget http://www.accellera.org/images/downloads/standards/systemc/systemc-2.3.1a.tar.gz
    tar -xzf systemc-2.3.1a.tar.gz && cd systemc-2.3.1a
    export SYSTEMC_HOME=`pwd`
    export TARGET_ARCH=linux64
    mkdir BUILD && cd BUILD
    ../configure --prefix=$SYSTEMC_HOME --enable-optimize --enable-static CXXFLAGS="-std=c++11"
    make -j 4 && make install
    
  3. Clone and build vcml. Make sure to set the environment variable VCML_HOME afterwards. vcml requires SystemC, but cmake should be able to locate it automatically if you have set SYSTEMC_HOME as indicated in the previous step:

    git clone https://github.com/janweinstock/vcml.git && cd vcml
    mkdir -p BUILD/RELEASE/BUILD && cd BUILD/RELEASE/BUILD
    cmake ../../.. -DCMAKE_INSTALL_PREFIX=.. -DCMAKE_BUILD_TYPE=RELEASE
    make -j 4 && make install
    export VCML_HOME=`pwd`/..
    
  4. Clone and build or1kiss. Make sure to set the environment variable OR1KISS_HOME afterwards as indicated below:

    git clone https://github.com/janweinstock/or1kiss.git && cd or1kiss
    mkdir -p BUILD/RELEASE/BUILD && cd BUILD/RELEASE/BUILD
    cmake ../../.. -DCMAKE_INSTALL_PREFIX=.. -DCMAKE_BUILD_TYPE=RELEASE
    make -j 4 && make install
    export OR1KISS_HOME=`pwd`/..
    
  5. Once the prerequisites are done, we can start building or1kmvp. First chose directories for building and deployment:

    <source-dir>  location of your repo copy,     e.g. /home/jan/or1kmvp
    <build-dir>   location to store object files, e.g. /home/jan/or1kmvp/BUILD
    <install-dir> output directory for binaries,  e.g. /opt/or1kmvp
    
  6. Configure and build the project. If you get an error, make sure the following environment variables are set correctly:

    • SYSTEMC_HOME (see step 2)
    • TARGET_ARCH (see step 2)
    • VCML_HOME (see step 3)
    • OR1KISS_HOME (see step 4)

    Configuration is done with cmake using the regular parameters:

    mkdir -p <build-dir>
    cd <build-dir>
    cmake <source-dir> -DCMAKE_INSTALL_PREFIX=<install-dir> -DCMAKE_BUILD_TYPE=RELEASE
    make -j 4 && make install
    
  7. After installing, the following new files and directories should be present:

    <install-dir>/bin/or1kmvp # simulator binary
    <install-dir>/config/     # directory holding example configuration files
    

    Note that in order to boot Linux, you will additionally need the kernel image, a compiled device tree and an initrd. These large binary files are not included in this repository, but can be found in the release list of this project.


Operation

To start simulation, you can run

<install-dir>/bin/or1kmvp -f <install-dir>/config/[up.cfg|smp2.cfg]

The up.cfg constructs a uniprocessor system, while smp2.cfg yields a dual core system. Note that, if you have built or1kmvp directly from source, you will additionally need Linux kernel images, compiled device tree files and an initrd and place them in <install-dir>/sw. These files are referenced by up.cfg and smp2.cfg, so you need to name them accordingly.


Networking

The simulator can run with networking support, if a tap device has been created before starting the simulation. Assuming one of the default platform config files is being used, you can run the following commands to enable networking:

sudo <install-dir>/bin/or1kmvp-tapnet start tap0
<install-dir>/bin/or1kmvp -f up.cfg
... use the simulator ...
sudo <install-dir>/bin/or1kmvp-tapnet stop tap0

From within the simulator, you can use arping, ping, wget etc. to test the network connection. In its default configuration, the host PC has the IP address 10.0.0.1 and the VP uses 10.0.0.2. The or1kmvp-tapnet utility also sets up NAT, allowing the simulator to connect to the internet using the host as a gateway.

From the host you can connect to a running simulator using telnet or ssh:

telnet 10.0.0.2
ssh [email protected]

Debugging

It is possible to connect GDB to a running simulation and investigate what each processor is doing. The debug context is bare-metal, meaning you will need a bare-metal debugger, i.e., or1k-elf-gdb. To connect to a VP running Linux, you can try the following (use port 55100 + coreid when running SMP):

or1k-gdb-elf <install-dir>/sw/vmlinux-4.20.0.elf
(gdb) target remote :55100
(gdb) ... do stuff on core 0...
(gdb) detach # disconnect
(gdb) target remote :55101
(gdb) ... do stuff on core 1...
(gdb) kill   # terminate simulation

By default, the processor will not wait for GDB and instead immediatly start executing code. To change that, you can use the -c system.cpu0.gdb_wait=1 command line switch to tell CPU0 to wait for GDB. Also note, that while an individual core is stopped, the SystemC simulation still continues and simulation time passes. To stop the entire simulation when a core is stopped by GDB, you can use -c system.cpu0.gdb_sync=1.

To debug software that is running within Linux, you can simply use the gdbserver utility with an active network connection between host and simulator (see Networking):

on the VP:
# gdbserver :54321 ./myprogram

on the host using or1k-linux-gdb:
(gdb) target remote 10.0.0.2:54321
(gdb) ... do stuff ...
(gdb) kill

Memory Map

This is the memory map of the system. Kernel device trees must be kept in sync with this.

0: 0x00000000 .. 0x07ffffff -> memory
1: 0x90000000 .. 0x90001fff -> uart8250
2: 0x92000000 .. 0x92001fff -> ethoc
3: 0x98000000 .. 0x98001fff -> ompic

Note that the default configuration for this system comes with 128MB of memory. You can increase this using the system.mem.size property (either via a config file or via the -c command line switch). If you change memory size, the default memory map will automatically adjust.


System Image

The Linux system uses dev/mmcblk0p1 as its root filesystem. You can either modify it directly from within the simulation (make sure sw/sdcard0.gpt is writable) or on your host PC. For the latter, do the following:

sudo losetup -f -P <install-dir>/sw/sdcard0.img # setup /dev/loopXX
losetup -a | grep sdcard0.gpt # figure out which loop device was used
# figure out which loop device was used, it should have two partitions p1/p2
sudo mount /dev/loopXXp1 /mnt
# make your changes in /mnt
sudo umount /mnt
sudo losetup -d /dev/loopXX # detach loop device

License

This project is licensed under the Apache-2.0 license – see the LICENSE file for details.

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