Getting Guix System to use llvmpipe

Getting Guix System to use llvmpipe

[Philip McGrath]

Hi folks,

I'm trying to install Guix System on real hardware for the first time, 
and I'm having some graphics trouble.

The machine has an older Asus M5A78L-M/USB3 motherboard with an onboard 
Radeon HD 3000 GPU---the R600 family, IIUC, so covered by the `radeon` 
driver rather than `amdgpu`. I understand that functionality will be 
limited since I'm not using nonfree firmware, and I can live with that.

I've tried Debian 11 on this board (without "nonfree"), and, after 
noting the missing firmware, it falls back to work acceptably with 
`llvmpipe`.

Unfortunately, Guix System is working less well. When it starts the 
display manager (I've tried both GDM and SDDM, with both X11 and 
Wayland), the screen goes blank permanently, and the logs show that 
starting the X server fails: initially with an error about an undefined 
symbol `exaGetPixmapDriverPrivate`, though through various incantations 
on the kernel command line or in the X configuration I can produce other 
errors, like "X: ../include/privates.h:121: dixGetPrivateAddr: Assertion 
`key->initialized' failed."

Can I configure Guix to give up on the missing firmware and just use 
`llvmpipe`, as Debian does?

Or, of course, if there's something even better I should do, I'd be glad 
to hear about that!

Thanks,
Philip

Re: Getting Guix System to use llvmpipe

[raingloom]

On Tue, 12 Oct 2021 12:52:46 -0400
Philip McGrath <philip@philipmcgrath.com> wrote:

> Hi folks,
> 
> I'm trying to install Guix System on real hardware for the first
> time, and I'm having some graphics trouble.
> 
> The machine has an older Asus M5A78L-M/USB3 motherboard with an
> onboard Radeon HD 3000 GPU---the R600 family, IIUC, so covered by the
> `radeon` driver rather than `amdgpu`. I understand that functionality
> will be limited since I'm not using nonfree firmware, and I can live
> with that.
> 
> I've tried Debian 11 on this board (without "nonfree"), and, after 
> noting the missing firmware, it falls back to work acceptably with 
> `llvmpipe`.
> 
> Unfortunately, Guix System is working less well. When it starts the 
> display manager (I've tried both GDM and SDDM, with both X11 and 
> Wayland), the screen goes blank permanently, and the logs show that 
> starting the X server fails: initially with an error about an
> undefined symbol `exaGetPixmapDriverPrivate`, though through various
> incantations on the kernel command line or in the X configuration I
> can produce other errors, like "X: ../include/privates.h:121:
> dixGetPrivateAddr: Assertion `key->initialized' failed."
> 
> Can I configure Guix to give up on the missing firmware and just use 
> `llvmpipe`, as Debian does?
> 
> Or, of course, if there's something even better I should do, I'd be
> glad to hear about that!
> 
> Thanks,
> Philip
> 

Just a hunch but maybe you could blacklist the broken firmware on the
kernel command line arguments. I think it's something like
modprobe.blacklist=radeon,amdgpu? Sorry, I can't look into it more
right now, but that should give you some keywords to search for and
maybe find the proper docs.

Re: Getting Guix System to use llvmpipe

[Philip McGrath]

On 10/12/21 4:09 PM, raingloom wrote:
> Just a hunch but maybe you could blacklist the broken firmware on the
> kernel command line arguments. I think it's something like
> modprobe.blacklist=radeon,amdgpu? Sorry, I can't look into it more
> right now, but that should give you some keywords to search for and
> maybe find the proper docs.

Thanks! This turned out not to work (I think parts of the radeon driver 
that don't depend on firmware may be used somehow?), but it set me down 
a path of looking for places to block things. After quite a bit of 
experimentation, I arrived at:

     (set-xorg-configuration
       (xorg-configuration
         (drivers
           '("fbdev" "vesa"))))

I don't know that it's optimal, and it doesn't feel especially elegant, 
but it was enough to get X working just now!

-Philip