The short answer is yes, QEMU can run on ARM processors. QEMU is an open source machine emulator and virtualizer that allows you to run operating systems and programs for one machine on a different machine. So QEMU can be used to run software compiled for x86 CPUs on an ARM device, and vice versa.
What is QEMU?
QEMU stands for Quick Emulator. As the name suggests, it provides efficient and fast emulation of entire guest hardware platforms like x86 PCs, ARM development boards, PowerPC systems etc. on a host system of a different architecture. QEMU emulates the CPU, memory, peripherals, storage, networking – everything necessary to run an operating system and apps. It works by dynamically translating instructions from the guest CPU architecture to instructions understood by the host CPU.
In addition to being an emulator, QEMU can also function as a virtualizer in conjunction with KVM kernel modules. In this mode, QEMU can take advantage of hardware extensions on the host for efficient virtualization. The guest Operating System still runs natively on the virtualized hardware provided by KVM as though it were physical hardware, providing near-native performance.
QEMU supports emulating a wide variety of CPU architectures like x86, x86-64, ARM, ARM64, MIPS, PowerPC, SPARC, RISC-V and more. It can run OSes like Linux, Windows, BSDs, Solaris, Android etc. This makes it a very versatile tool for cross-platform development and testing.
Running QEMU on ARM
Since QEMU itself is just a user-space application, it can be compiled to run on any architecture supported by it, including ARM. So you can run QEMU on ARM boards like the Raspberry Pi to emulate other architectures. Here are some ways QEMU is commonly used on ARM devices:
1. Emulate x86 on ARM
A common use case is running x86 guests like Windows or Linux on ARM SBCs like the Pi. The x86 system runs entirely in software emulation so is slower than native speed, but usable for testing purposes.
For example, to run an x86_64 Linux VM on a Raspberry Pi 4, first install QEMU on the Pi: sudo apt update sudo apt install qemu-system-x86 qemu-utils
Then launch a Linux guest image with: qemu-system-x86_64 -enable-kvm -m 2048 -cpu host -drive file=/path/to/disk.img,if=virtio -cdrom /iso/image.iso
This will boot an x86_64 VM using KVM for acceleration if available. You can also run x86 Windows guests this way.
2. Emulate ARM on ARM
QEMU on ARM can also be used to emulate other ARM platforms. For example, you may want to run ARM64 guests on an ARMv7 host, or vice versa. Launching an AArch64 guest on the Pi: qemu-system-aarch64 -M raspi3 -kernel kernel8.img -drive file=debian_arm64.img,if=sd,format=raw
This boots a 64-bit kernel with ARM64 root filesystem image, emulated on the 32-bit Raspi3 machine model. The performance is near native since both host and guest are ARM platforms.
3. User-mode emulation
In addition to full system emulation, QEMU on ARM can also be used for user-mode emulation of foreign binaries using the qemu-user binaries. For example: qemu-x86_64 -L /usr/x86_64-linux-gnu/ ./x86_binary
This will execute the x86-64 binary on ARM using QEMU’s user-mode emulation, by providing the necessary x86_64 Linux userland libraries.
Performance of QEMU on ARM
The performance you can expect from QEMU on ARM depends on the type of emulation:
- Full system emulation – When emulating a completely different architecture like x86 on ARM, performance takes a major hit due to instruction translation and lack of hardware acceleration. Expect guest performance to be anywhere from 5-10x slower than native machine speed.
- KVM with ARM guests – If using KVM and virtio paravirtualized drivers, the performance penalty for running ARM guests on ARM hosts is very low. Guest performance is nearly the same as host performance since both are ARM platforms.
- User-mode emulation – Performance for foreign binaries under qemu-user is better than full system emulation since only the CPU and memory access are emulated. Performance penalty may be 2-3x slower at worst.
So while QEMU on ARM can run heavier tasks like x86 VMs, it works best for lighter workloads like user-mode emulation, or with KVM acceleration for ARM guests. For the heavy lifting, you’ll want to use a faster x86 machine as the QEMU host.
Use Cases for QEMU on ARM
Here are some of the popular use cases and scenarios where running QEMU on ARM devices makes sense:
- Mobile/Embedded Development – Emulate the hardware that your software will run on during development using QEMU on your ARM dev machine.
- Cross-platform Testing – Test builds for other architectures like x86 or MIPS using QEMU user-mode emulation on your ARM system.
- Kernel Development – Build and test kernels for other architectures by booting them under QEMU on your ARM board.
- Application Porting – Run x86/ARM Windows or Linux apps on ARM/x86 using QEMU for quick porting and testing.
- Education/Tutorials – Learn how different architectures behave by running them on your ARM system with QEMU.
While native solutions are always faster, running QEMU on ARM enables scenarios like the above at low cost and convenience when you may not have access to the actual hardware.
Limitations of QEMU on ARM
There are certain limitations to be aware of when using QEMU on ARM boards:
- Performance will always be lower than native hardware, especially for cross-architecture emulation.
- No accelerated graphics – Graphics will be software emulated and slow.
- Limited RAM/storage on ARM SBCs to run heavyweight guests.
- No PCI device passthrough support for USB/Disk controllers etc.
- Emulated system feels ‘laggy’ compared to real hardware.
- Not all guest architectures may be emulated well or usable.
So while QEMU on ARM enables exciting use cases, it is no replacement for real hardware which will be faster. Performance expectations must be set accordingly when using QEMU on ARM boards.
Optimizing QEMU Performance on ARM
Here are some tips to optimize QEMU performance on your ARM device:
- Use KVM to accelerate ARM guests if your host kernel supports it.
- Enable virtio paravirtualized drivers in guests for better I/O performance.
- Use lighter OS images or cut down bloat for better experience.
- Allocate more RAM and cores to QEMU process if available.
- Use JIT translation modes or KVM TCG for better code translation.
- Store guest images on faster storage like SSD rather than SD cards.
- Tune guest OS for better performance – disable heavy desktops etc.
You can also benchmark and tweak QEMU performance by changing CPU model, HTM, VFP usage and other emulator options. Despite optimizations, expect a large performance gap compared to native hardware.
Conclusion
QEMU is a very versatile emulator that can definitely run on ARM devices like Raspberry Pi boards to emulate other hardware platforms. While the performance is not comparable to native hardware, QEMU on ARM enables useful development, testing and educational use cases at low cost and convenience.
For the best experience, use QEMU’s KVM virtualization if available, run lighter guests, and optimize host and guest settings. Performance expectations should be adjusted accordingly based on workload. Overall, QEMU provides an invaluable tool to emulate different hardware on ARM even if limited by the specs of SBCs.
