bug#22633: Provide a kvm-less qemu / guix system vm

[Ludovic Courtès]

Christopher Allan Webber <address@hidden> skribis:

> Christopher Allan Webber writes:
>
>> Ludovic Courtès writes:
>>
>>> Libkmod honors ‘modprobe.blacklist’ (in ‘kcmdline_parse_result’ in
>>> libkmod-config.c) and eudev passes KMOD_PROBE_APPLY_BLACKLIST
>>> unconditionally in udev-builtin-kmod.c (meaning it honors it too.)
>>>
>>> However, there’s a hyphen-vs-underscore issue, I think.  Namely, the
>>> file is called ‘kvm-intel.ko’, but the normalized module name is
>>> ‘kvm_intel’, and this is what libkmod expects (commit 5c7dd5a changes
>>> our code to normalize module names similarly.)
>>>
>>> Could you try with “modprobe.blacklist=kvm_intel”?
>>
>> I tried it, and it works!  This does mean that /dev/kvm doesn't exist,
>> so I should be able to write a patch to Guix that disables kvm for qemu
>> when /dev/kvm is absent.  Great! :)
>
> This is slightly based off of Leo's preliminary patch, so I included him
> in the copyright headers.  I've tested and it works (in terms of
> disabling kvm if no /dev/kvm is present) here.

Cool!  Can you just double-check whether -enable-kvm has any effect when
/dev/kvm is missing?  If it has no effect when /dev/kvm is missing, then
we don’t even need a patch.

> Let me know if I need to fix something or if I should push...
>
> From 852e0049213a0a80cacdcad4aba13ab242c3fbd8 Mon Sep 17 00:00:00 2001
> From: Christopher Allan Webber <address@hidden>
> Date: Mon, 22 Feb 2016 11:23:14 -0800
> Subject: [PATCH] vm: Only pass "-enable-kvm" to qemu if /dev/kvm is present.
>
> * gnu/build/vm.scm (load-in-linux-vm): Only pass "-enable-kvm" flag to qemu
>   if "/dev/kvm" is present.
> * gnu/system/vm.scm (common-kvm-options): Same as above.

[...]

> +                   ;; Only enable kvm if we see /dev/kvm exists.
> +                   ;; This allows uers without hardware virtualization to 
> still use these
                                     ^^
Typo.

[...]

> +     ;; Only enable kvm if we see /dev/kvm exists.
> +     ;; This allows uers without hardware virtualization to still use these

Ditto.

Otherwise the patch LGTM.  Make sure to mention:

  Fixes <http://bugs.gnu.org/22633>.

in the commit log.

Thanks,
Ludo’.