Fedora on Raspberry PI updates

Some updates for the Running Fedora on the Raspberry PI 2 article.

There has been great progress on getting the Raspberry PI changes merged upstream in the last half year. u-boot has decent support meanwhile for the whole family, including 64bit support for the Raspberry PI 3. Raspberry PI 2 support has been merged upstream during the 4.6 merge window. It looks like Raspberry PI 3 will follow in the next (4.7) merge window. Time to have a closer look at all this new stuff.

arm images

There are two different kinds of arm images now:

First arm-rpi2-f23-foundation. They are using a kernel built from the tree maintained by the Raspberry PI Foundation at github. They are like the older ones, just with newer packages. The kernels are booted directly by the firmware.

Second arm-rpi2-f23-mainline. They are using a mainline kernel, with a few patches on top for Raspberry PI 3 support (device tree, 64bit, wifi). I expect the number of patches will decreate quickly as things get merged mainline with the next merge windows. The kernel is booted using u-boot. On the Raspberry PI 3 it’ll boot a 64bit kernel (with 32bit userspace) by default. If you don’t want that you can just run “dnf remove uboot-rpi3-64“, which will remove both 64bit uboot and kernel, then reboot.

There are no big differences between the two images types. At the end of the day it is just a different set of packages. You can move from foundation kernels (package name “kernel-rpi2” to mainline kernels (package names “kernel-main” and “kernel-main64“) and back without problems. Having them installed in parallel works fine too. The foundation kernels set kernel= in config.txt in postinstall, so one just needs to install and reboot. Switching to mainline is done by installing them, then commenting out the kernel= line in config.txt. Next boot will load uboot then, which in turn loads the mainline kernel.

arm64 images

While looking at the image directory you might have noticed the arm64-rpi3-f23-mainline image. That is a full 64bit (aka aarch64) build, with both 64bit kernel and userspace. Will boot on the Raspberry PI 3 only, for obvious reasons.

kvm

There is progress with kvm too. Recent firmware loads the kernel in hyp mode, so the hypervisor extensions are available to the linux kernel. Also it seems the kvm core and irqchip (GIC) emulation are separated now. kvm initializes successfully, but the kernel doesn’t provide irqchip because the Raspberry PI hasn’t a GIC. Result is this:

[kraxel@pi-dpy ~]$ sudo lkvm run
# lkvm run -k /boot/vmlinuz-4.5.1-103-rpi2 -m 448 -c 4 --name guest-10565
Error: Unsupported KVM extension detected: KVM_CAP_IRQCHIP
Fatal: Failed to create virtual GIC

So, userspace can’t deal with the missing GIC emulation (qemu fails too). But it looks like by doing GIC emulation in userspace it should be possible to run kvm on the Raspberry PI.

3 thoughts on “Fedora on Raspberry PI updates

  1. =w=

    Why arm64-rpi3-f23-mainline-20160421.raw.xz can’t be downloaded? It shows “don’t have permission to access”.

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