Re: "make run-qemu" gets Wayland protocol error

[Demi Marie Obenour <demiobenour@gmail.com>]

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On 7/20/25 04:20, Alyssa Ross wrote:
> Alyssa Ross <hi@alyssa.is> writes:
> 
>> Demi Marie Obenour <demiobenour@gmail.com> writes:
>>
>>> On 7/20/25 03:55, Alyssa Ross wrote:
>>>> Demi Marie Obenour <demiobenour@gmail.com> writes:
>>>>
>>>>> If I run `make run-qemu` under a Wayland compositor (tested with both
>>>>> Sway and Weston), I get a Wayland protocol error ("invalid object 0")
>>>>> and QEMU exits.  It appears that there is a problem with
>>>>> wayland-proxy-virtwl.  I get the following error from foot:
>>>>>
>>>>> warn: main.c:437: 'C' is not a UTF-8 locale, falling back to 'C.UTF-8'
>>>>> warn: config.c:3520: no configuration found, using defaults
>>>>> Fontconfig warning: no <cachedir> elements found. Check configuration.
>>>>> Fontconfig warning: adding <cachedir>/var/cache/fontconfig</cachedir>
>>>>> Fontconfig warning: adding <cachedir prefix="xdg">fontconfig</cachedir>
>>>>>  err: wayland.c:1714: no compositor
>>>>>  err: wayland.c:2248: failed to flush wayland socket: Connection reset by peer
>>>>>
>>>>> And the following from wayland-proxy-virtwl:
>>>>>
>>>>> 2025-07-20 02:14:48.638    wl-proxy [WARNING]: Error handling client: Invalid_argument("invalid bounds in Cstruct.LE.get_uint32 [0,0](4096) off=0 len=4")
>>>>
>>>> This is partially fixed with <https://github.com/NixOS/nixpkgs/pull/419860>,
>>>> which is more recent than Spectrum's pinned Nixpkgs.  I expect to
>>>> update that in the next few days, but until then, you can apply it on
>>>> top of the Nixpkgs revision in lib/nixpkgs.default.nix, and then pass
>>>> --arg config '{pkgsFun = import /path/to/nixpkgs;}' to any Spectrum
>>>> Nix command.
>>>>
>>>> With that change, I'm able to run foot fine in QEMU.  gnome-text-editor
>>>> runs but prints errors and looks weird, and Firefox doesn't even start.
>>>> crosvm built from the same tag as rutabaga_gfx used by QEMU works fine,
>>>> so I think it must be a QEMU bug.  I spent some time yesterday trying to
>>>> debug it, but didn't get anywhere so far.  If I can't figure it out soon
>>>> I'll open an upstream bug report.
>>>
>>> That's a good idea.  Would it be possible to use vhost-user as a
>>> workaround?  That would use crosvm's implementation instead.
>>
>> No.  crosvm and QEMU have different ideas of what vhost-user-gpu.
>> QEMU expects to provide all the graphical stuff itself, using the
>> vhost-user-gpu protocol[1], whereas the crosvm one has the backend do
>> almost everything (like every other vhost-user device — also much better
>> for sandboxing).
>>
>> [1]: https://www.qemu.org/docs/master/interop/vhost-user-gpu.html#vhost-user-gpu-protocol
> 
> Possibly the best way to test this would be to use crosvm, which also
> supports virtio-sound.

I thought the only implemented backends were CrAS and Android.
-- 
Sincerely,
Demi Marie Obenour (she/her/hers)

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