On Fri, Apr 10, 2020 at 04:38:37PM +0200, Ludovic Courtès wrote:
> > +     (if (member (%current-system) '("x86_64-linux" "i686-linux"))
> > +         ;; Load uvesafb to show installer when no KMS is available.
> > +         `(,(service kernel-module-loader-service-type '("uvesafb"))
> > +           [...]
> 
> This is not quite correct because here ‘%current-system’ is evaluated at
> the top level, when (gnu tests install) is loaded.  So on my laptop,
> it’s always "x86_64-linux", regardless of any ‘-s’ flags.  Also, it
> ignores ‘--target’.
> 
> Can we arrange to make it unconditional?
> 
> One way to do that (not great), would be to make it an activation
> snippet: since activation snippets are written as monadic code, we can
> reliably check ‘%current-system’ & ‘%current-target-system’ from there.
> (For lack of a solution like <https://issues.guix.gnu.org/issue/29296>.)

Please consider the attached patch.  I chose to go without
kernel-module-loader-service (only copying its requirements field)
because I do not know how to conditionally extend or start another
Shepherd service from an activation snippet.

I tested it on QEMU with and without nomodeset.  With a previous Guix
System install image, it stayed black when adding a nomodeset kernel
parameter.  I will test again on real hardware now, but previous
testing of uvesafb-enabled installer images proved successful unlike
non-uvesafb images.

Feel free to adapt the patch or not include it.  Or tell me to change
it if there is time.

Regards,
Florian