On Thu, May 07, 2020 at 11:12:34AM +0300, Efraim Flashner wrote:
> I haven't tested the produced image, but the following builds without
> trying to also build v86d
> 
>          (start
>            (if (and (and (string-suffix? "linux-gnu" %host-type)
>                          (or (string-prefix? "x86_64" %host-type)
>                              (string-prefix? "i686" %host-type)))
>                     (file-exists? "/dev/fb0"))
>              #~(lambda ()
>                  ;; uvesafb is only supported on x86 and x86_64.
>                  (invoke #+(file-append kmod "/bin/modprobe")
>                          "uvesafb"
>                          (string-append "v86d=" #$v86d "/sbin/v86d")
>                          "mode_option=1024x768"))
>              #~(lambda () #t)))

This way uvesafb is started unconditionally on x86_64, even when it is
not needed, leading to video corruption on some boots in QEMU.

I have more success with moving the file-exists check into the
#~(lambda …) like the attached patch.  But I’m not sure it really
fixes ARM builds.

I tested via

qemu-system-x86_64 -m 1024 -smp 1 -enable-kvm -nic user,model=virtio-net-pci -boot menu=on,order=d -drive media=cdrom,file=/gnu/store/0cgbp4y7awk4spg49ajw077xyzk24fi0-iso9660-image

and on hardware.  With QEMU, uvesafb is needed if and only if
nomodeset is passed as a kernel parameter.

Now how to build an ARM image for QEMU?

Sorry I left such a mess with uvesafb.

Regards,
Florian