Re: black screen troubles trying to boot with Xen Hypervisor grub option

[Jamie Campbell <jamie@xxxxxxxx>]

On 2023-07-10 3:47 p.m., zithro wrote:
> On 10 Jul 2023 19:02, Jamie Campbell wrote:
> > I tried load_video, serial disable, and diverting I still got black 
> > screen but then I tried your suggestion of going into BIOS and just 
> > totally suppressing EFI and forcing the system to do strictly legacy 
> > stuff and now it actually boots!  I'm curious as to whether the EFI 
> > approach could still get to a bootable system, but not curious enough 
> > to re-break it and be stuck again.  Thanks for getting me to 
> > bootability!
> > -Jamie
> (Please bottom-post (; )
>
> I had the same problem booting Xen+Debian on UEFI, found a solution, 
> maybe it applies to you ?
> The problem started when I updated dom0 from Stretch to Buster (at the 
> time Buster became stable). With the new version of 
> "/etc/grub.d/20_linux_xen", no more boot.
> If you compare the old (stretch) and the actual files (from buster 
> on), some changes are about multiboot/module to multiboot2/module2 and 
> in the check you pointed ($grub_platform isn't "pc").
> But as you may have eliminated the $grub_platform problem, maybe it's 
> the use of multiboot versus multiboot2 ?
> What I would do is move or rename "/etc/grub.d/20_linux_xen", and then 
> try with the Stretch version of the file.
> (If just renaming, I recommend you to edit the "title" stanzas to 
> better identify the menus : you'd have identical lines).
> If you want to rambo edit "20_linux_xen" in place, below you will find 
> the concerning differences between two versions.
> Basically replace ${xen_loader} and ${module_loader} by respectively 
> multiboot and module.
> I'm still booting a bookworm dom0 with multiboot/module, YMMV !
>
> ---
> WORKING VERSION
> [...]
> if [ "\$grub_platform" = "pc" -o "\$grub_platform" = "efi" -o 
> "\$grub_platform" = "" ]; then
>             xen_rm_opts=
>         else
>             xen_rm_opts="no-real-mode edd=off"
>         fi
>     multiboot    ${rel_xen_dirname}/${xen_basename} placeholder 
> ${xen_args} \${xen_rm_opts}
>     echo    '$(echo "$lmessage" | grub_quote)'
>     module    ${rel_dirname}/${basename} placeholder 
> root=${linux_root_device_thisversion} ro ${args}
> [...]
>     module    --nounzip   ${rel_dirname}/${initrd}
> [...]
>
> ---
> NON-WORKING VERSION
> [...]
> if [ "\$grub_platform" = "pc" -o "\$grub_platform" = "" ]; then
>             xen_rm_opts=
>         else
>             xen_rm_opts="no-real-mode edd=off"
>         fi
>     ${xen_loader}    ${rel_xen_dirname}/${xen_basename} placeholder 
> ${xen_args} \${xen_rm_opts}
>     echo    '$(echo "$lmessage" | grub_quote)'
>     ${module_loader}    ${rel_dirname}/${basename} placeholder 
> root=${linux_root_device_thisversion} ro ${args}
> [...]
>     ${module_loader}    --nounzip   ${rel_dirname}/${initrd}
> [...]
> if ($grub_file --is-x86-multiboot2 $current_xen); then
>     xen_loader="multiboot2"
>     module_loader="module2"
>     else
>     xen_loader="multiboot"
>     module_loader="module"
>     fi
> [...]
I re-installed with EFI stuff on again, tested that it black screens the 
same was as before, then removed the 2s (module, multiboot) and did a 
reboot, and it locks up when it gets to "Loading initial ramdisk", and 
also warns that "no console will be available to OS".  I'll go back to 
legacy again, but it was worth a shot, thanks for the suggestion, and 
sorry for the netiquette oops!
-Jamie