How to emulate the Raspberry Pi 2 on QEMU?

Question

Some time ago I emulated the Raspberry Pi following this article, but this approach has several problems:

1. It is very slow.
2. The display solution is limited

Answer 1

Ubuntu 16.04, QEMU 2.9.0 -M raspi2, Raspbian 2016-05-27, vanilla kernel

1. Compile QEMU 2.9.0 from source:

   sudo apt-get build-dep qemu-system-arm
   git clone --recursive git://git.qemu-project.org/qemu.git
   cd qemu
   git checkout v2.9.0
   ./configure
   make `nproc`
   

2. Download image and extract the kernel and dts from it:

   1. Download the image and unzip it:

      wget http://downloads.raspberrypi.org/raspbian/images/raspbian-2016-05-31/2016-05-27-raspbian-jessie.zip
      unzip 2016-05-27-raspbian-jessie.zip
      

   2. Mount the second image of the partition. The easiest way is:

      sudo losetup -f --show -P 2016-05-27-raspbian-jessie.img
      

      This only works with latest losetup on Ubuntu 16.04, other methods at: https://askubuntu.com/questions/69363/mount-single-partition-from-image-of-entire-disk-device/496576#496576

      This prints a loop device, e.g.:

      /dev/loop0
      

      so we do:

      sudo mkdir /mnt/rpi
      sudo mount /dev/loop0p1 /mnt/rpi
      cp /mnt/rpi/kernel7.img .
      cp /mnt/rpi/bcm2709-rpi-2-b.dtb .
      sudo umount /mnt/rpi
      sudo losetup -d /dev/loop0
      

3. Run:

   ./arm-softmmu/qemu-system-arm \
       -M raspi2 \
       -append "rw earlyprintk loglevel=8 console=ttyAMA0,115200 dwc_otg.lpm_enable=0 root=/dev/mmcblk0p2" \
       -cpu arm1176 \
       -dtb bcm2709-rpi-2-b.dtb \
       -sd 2016-05-27-raspbian-jessie.img \
       -kernel kernel7.img \
       -m 1G \
       -smp 4 \
       -serial stdio \
   ;
   

You can then login on the terminal that shows on your host terminal.

Current limitations:

• -M raspi2 was added in QEMU 2.6.0, and Ubuntu 16.04 only has QEMU 2.5.0, so we have to compile QEMU from source. But this is not hard.
• the GUI shows but is not responding to the mouse / keyboard, tested on both SDL and VNC. But CLI works perfectly however. So you might as well use the Lite image which has go GUI for now.
• no networking

Ubuntu 16.04, QEMU 2.5.0, Raspbian 2016-05-27, modified kernel

This method uses -M versatilepb which is present on the QEMU 2.5.0 of Ubuntu 16.04.

The downside is that you have to download a modified kernel (see https://raspberrypi.stackexchange.com/questions/47124/emulating-with-qemu-why-the-extra-kernel), and modify the image, so it is less representative of the real system.

1. Download: https://github.com/dhruvvyas90/qemu-rpi-kernel/blob/36ede073f4ccb64f60200ede36c231afe9502070/kernel-qemu-4.4.12-jessie

   We pick 4.4.12 since that is the kernel version in the Raspbian image.

   The process to generate that kernel blob is described at in the repository at: https://github.com/dhruvvyas90/qemu-rpi-kernel/tree/36ede073f4ccb64f60200ede36c231afe9502070/tools

   Why this extra kernel image is needed: https://raspberrypi.stackexchange.com/questions/47124/emulating-with-qemu-why-the-extra-kernel

2. Modify the Raspbian image as mentioned at: https://github.com/dhruvvyas90/qemu-rpi-kernel/wiki/Emulating-Jessie-image-with-4.x.xx-kernel/0068f0c21d942b0f331e18014ff8e22c20cada5c

   Summary:

   1. Mount the image just as we did for the -M raspi2, but use the second partition instead of the first:

      sudo mount /dev/loop0p2 /mnt/rpi
      

   2. Edit the image:

      # Comment out the line present there with #
      sudo vim /mnt/rpi/etc/ld.so.preload
      # Comment out the lines of type: "/dev/mmcblk*"
      sudo vim /mnt/rpi/etc/fstab
      

3. Run:

   sudo apt-get install qemu-system-arm
   qemu-system-arm \
       -kernel kernel-qemu-4.4.12-jessie \
       -cpu arm1176 \
       -m 256 \
       -M versatilepb \
       -no-reboot \
       -serial stdio \
       -append "root=/dev/sda2 panic=1 rootfstype=ext4 rw" \
       -hda 2016-05-27-raspbian-jessie.img
   

[failed] Ubuntu 17.04, QEMU 2.8.0 -M raspi2, Raspbian 2016-05-27, vanilla kernel

On this newer Ubuntu, QEMU 2.8.0 is the default, so we don't need to compile QEMU from source for -M raspi2. However, 2.8.0 hangs on boot after the message:

Console: switching to colour frame buffer device 100x30

This goes to show how unstable -M raspi2 still is.

[failed] Ubuntu 16.04, QEMU 2.9.0 -M raspi2, Raspbian 2017-08-16, vanilla kernel

On this newer image, using the same method for 2016-05-27, the kernel panics at boot with:

Please append a correct "root=" boot option; here are the available partitions:
...
[    4.138114] ---[ end Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0)

TODO: sschoof mentions that rootdelay=1 solves this, I have to try it out.

bztsrc/raspi3-tutorial RPI3 bare metal on QEMU

https://github.com/bztsrc/raspi3-tutorial is a good set of examples that just work on QEMU, ultraquick getting started at: https://raspberrypi.stackexchange.com/questions/34733/how-to-do-qemu-emulation-for-bare-metal-raspberry-pi-images/85135#85135

Answer 2

If you're comfortable building qemu, you can find support for pi2 system emulation here: https://github.com/0xabu/qemu. It's not particularly speedy, and the device emulations are incomplete, but you can resize the RAM and framebuffer.

There are brief instructions for booting Raspbian at the end of https://github.com/0xabu/qemu/wiki

Answer 3

If you want to run a Raspberry Pi 2 build bot or something similar you should take a look at running Qemu in user/static mode. I tried this using Linux in a virtual machine, it's quite fast compared to Qemu system emulation. Unfortunately it only emulates the CPU so you won't be able to test games or Wayland/Weston.

I was able to build a kernel for my Pi 2 in roughly a hour using this method.