QEMU¶

Running Applications¶

Building QEMU¶

Additional packages and plugins

Refer to the official documentation for details about installing additional packages and enabling support of QEMU plugins.

Install necessary packages for Arch:

sudo pacman -S git cmake ninja gperf ccache dfu-util dtc wget            \
               python-pip python-setuptools python-wheel xz file make

Install necessary packages for Fedora:

sudo dnf group install "Development Tools" "C Development Tools and Libraries"
dnf install git cmake ninja-build gperf ccache dfu-util dtc wget         \
            python3-pip xz file glibc-devel.i686 libstdc++-devel.i686

Install necessary packages for Ubuntu:

sudo apt-get install --no-install-recommends git cmake ninja-build gperf \
                     ccache dfu-util device-tree-compiler wget           \
                     python3-pip python3-setuptools python3-wheel        \
                     xz-utils file make gcc gcc-multilib

Install necessary packages for Void:

sudo xbps-install git cmake ninja gperf ccache dfu-util dtc wget  \
                  python3-pip python3-setuptools python3-wheel xz \
                  file make

Then prepare sources and a build directory:

git clone https://github.com/foss-for-synopsys-dwc-arc-processors/qemu
mkdir -p qemu/build
cd qemu/build

Configure QEMU inside of the build directory (use your own --prefix value for installation path):

../configure --target-list=arc-softmmu,arc64-softmmu,arc-linux-user,arc64-linux-user \
             --prefix=/tools/qemu --enable-debug --enable-debug-tcg --enable-trace-backends=simple \
             --disable-plugins --skip-meson --disable-pie

If you face an error then consider using --disable-werror configure option to try to eliminate it. Also, consider reporting a bug on toolchain's GitHub page.

What options are responsible for what:

--target-list=arc-softmmu,arc64-softmmu,arc-linux-user,arc64-linux-user — build QEMU both for these targets:
qemu-system-arc — system emulation for ARC HS3x/4x/5x processors family;
qemu-system-arc64 — system emulation for ARC HS6x processors family;
qemu-arc — user space Linux emulation for ARC HS3x/4x/5x processors family;
qemu-arc64 — user space Linux emulation for ARC HS6x processors family.
--prefix=/tools/qemu — an installation path.
--enable-debug --enable-debug-tcg --enable-trace-backends=simple --disable-plugins — options for development needs.
--enable-trace-backends=simple — for tracing (described in [[Profiling with QEMU]]).
--skip-meson — do not run Meson on every build.
--disable-werror — in case QEMU emits unexpected warnings.
--disable-pie — needed for older GCC (like in CentOS 7).

Build and install:

make
make install

Configure your environment:

export QEMU_HOME="/tools/qemu"
export PATH="${QEMU_HOME}/bin:$PATH"

Enhanced Logging¶

To enable logging, it is necessary to provide the enabled log levels with the -d flag. Some of the more relevant ones are:

in_asm          show target assembly code for each compiled TB
nochain         do not chain compiled TBs so that "exec" and "cpu" show complete traces
exec            show trace before each executed TB (lots of logs)
cpu             show CPU registers before entering a TB (lots of logs)
fpu             include FPU registers in the 'cpu' logging
int             show interrupts/exceptions in short format
mmu             log MMU-related activities
unimp           log unimplemented functionality

To get a complete listing, run qemu-system-arc -d help. Use -D <logfile> to dump the logs into a file instead of standard output.

Tracing Internals¶

QEMU provides a tracing infrastructure which may help in debugging or analyzing what happens within a simulation cycle. At this moment, there are two tracers added into ARC backend, one for MMU operations, and another for exceptions:

# mmu.c
mmu_command(uint32_t address, const char *command, uint32_t pd0, uint32_t pd1) "[MMU] at 0x%08x, CMD=%s, PD0=0x%08x, PD1=0x%08x"

# helper.c
excp_info(uint32_t address, const char *name) "[IRQ] at 0x08, Exception=%s"

Firstly, build QEMU with the --enable-trace-backends=simple configure parameter. Then Create a file with the events you want to trace. For example, here is such file with name events.trc:

mmu_command
excp_info

Run the virtual machine to produce a trace file:

qemu-system-arc --trace events=events.trc ...

Pretty-print the binary trace file (override <pid> with QEMU process id for you session):

<QEMU-source-tree-path>/scripts/simpletrace.py <QEMU-source-tree-path>/target/arc/trace-events trace-<pid>

Running Tests¶

TCG is the internal language that powers QEMU. There are some assembly tests that validate the basic function of several instructions in QEMU.

Firstly, make sure that QEMU if configured with --cross-cc-arc=arc-elf32-gcc and --cross-cc-arc64=arc64-elf-gcc options. Then after building QEMU use these commands to run TCG tests:

make clean-tcg
make build-tcg
make check-tcg