Re: A few Machines crash when "no default audio driver available"

["Daniel P. Berrangé" <berrange@redhat.com>]

On Thu, Jul 09, 2026 at 03:22:05PM +0200, Markus Armbruster wrote:
> Cc: mainainters for "Overall Audio backends"
> Peter Maydell <peter.maydell@linaro.org> writes:
> 
> > On Thu, 9 Jul 2026 at 12:44, Markus Armbruster <armbru@redhat.com> wrote:
> >>
> >> I stumbled over ARM machine musicpal, PPC machines pegasos1, pegasos2,
> >> and MIPS machine fuloong2e crashes.
> >>
> >> I run them like this:
> >>
> >> $ qemu-system-aarch64 -M musicpal -nodefaults -S -display none -monitor stdio
> >
> >> Died when device_set_realized() tried to propagate a "no default audio
> >> driver available" error to &error_abort.
> >
> > Is this something we want to have be a possibility the devices
> > have to cope with? Can we have the "ignores all audio data"
> > backend be always available instead?
> 
> There's plenty of precedence for /dev/null-like backends.
> 
> > Otherwise every audio device needs to cope with "there is no
> > audio backend available" and implement "do nothing with the
> > audio data" itself.
> 
> Yes.

We've got a bit of tension between "no defaults" and "builtin audio
devices" here.

Cnosider if I had instead done

  qemu-system-x86_64 -M pc -device ac97 -nodefaults

It is not unreasonable to expect to see an error because you asked
explicitly for 'ac97'  and forgot to wire up the required audio
backend, and asked to NOT have any defaults.

But with your 'musicpal' machine example, you never asked for the
frontend device, so you should be forgiven for also not asking
for a audio backend.

If we guarantee a /dev/null audio backend always exists, we help
the second case but degrade the first case

So we must pick the lesser evil :-(

With regards,
Daniel
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