Installing qemu-binfmt with support for emulating the host architecture breaks everything

Hey y'all,

I recently setup virtualization on my Guix machine (both libvirt and qemu, for different purposes). While configuring libvirt (via virt-manager), I got a bit confused about how to make things work and also installed qemu-binfmt for x86_64, the host architecture. Upon my next reboot, however, I reached a fully-booted TTY and was unable to do anything else. GDM was not launching, and if I attempted to login to the TTY itself, I was greeted by an error message like the following:

"cannot execute /gnu/store/path-to-something/bin/thing: Too many layers of symlinks"

After some misadventures, I have finally narrowed down that the cause of this issue was having x86_64 in the list of qemu-binfmt-configuration platforms while running on x86_64. I assume that including the host architecture in the list of platforms for qemu-binfmt will do this regardless of architecture, but cannot currently test this.

Here's what I believe to be a minimum reproducible example for x86_64:

```

(operating-system

...

(services (cons*

(service qemu-binfmt-service-type

(qemu-binfmt-configuration

(platforms (lookup-qemu-platforms "x86_64"))))

...)

...)

```

Good luck,

Juli

Hi Guix!

I can confirm that this issue is still around and still causing

headaches! ;)

It's definitely a problem on the aarch64 architecture. It's probably

safe to say it's a problem on every platform.

Given how cryptic this error is and how easily it can sneak up in more

complicated system configurations ([1] and [2]), we should capture this

mistake sometime during the build process. Even if putting the target

system as a QEMU emulation platform doesn't make sense, a broken system

with no helpful diagnostics isn't a proportional consequence.

[1]: https://lists.gnu.org/archive/html/help-guix/2023-03/msg00121.html

[2]: https://lists.gnu.org/archive/html/help-guix/2024-05/msg00160.html

--

Take it easy,

Richard Sent

Making my computer weirder one commit at a time.