[libvirt] guests and pulseaudio fighting over audio devices
Dave Allan
dallan at redhat.com
Thu Sep 17 14:00:29 UTC 2009
Daniel P. Berrange wrote:
> On Tue, Sep 15, 2009 at 04:45:31PM -0400, Dave Allan wrote:
>> I noticed that when a KVM guest created with virt-manager is running on
>> F10, sound on the physical host stops working. When all VMs are
>> shutdown, sound starts working again. Removing the <sound> tag from the
>> VM XML allows sound to work while the VM is booted. To further
>> complicate troubleshooting, if audio is already playing when the guest
>> is started it keeps playing, since pulse already has the device open.
>>
>> The message in /var/log/messages when I try to play audio is:
>>
>> pulseaudio[6492]: module-alsa-sink.c: Error opening PCM device front:0:
>> Device or resource busy
>>
>> strace of pulseaudio shows:
>>
>> open("/dev/snd/pcmC0D0p", O_RDWR|O_NONBLOCK) = -1 EBUSY (Device or
>> resource busy)
>>
>> but fuser and lsof show nothing. A trivial test program also sees
>> Device or resource busy when trying to open /dev/snd/pcmC0D0p
>>
>> I am in favor of removing the <sound> tag from the default
>> configuration, since I don't use sound from within guests and I do use
>> sound on my desktop, but perhaps this behavior is specific to my
>> configuration. I haven't investigated it exhaustively. What does
>> everybody else think?
>
> It is complicated :-) In Fedora >= 11 we currently disable all use of
> sound cards, but this upsets people who want sound ;-P I'm working
> on a new version of the patch which sets up audio-over-VNC, while for
> SDL allows the host audio backend to be used & configured.
>
> I still need to finish my GTK-VNC patches to do the client end of
> audio over VNC, then it'll all play correctly with desktop audio
> services via gstreamer/pulseaudio
Sounds good--I'm looking forward to it (not that I really use sound in
VMs, but that sounds like the right way to do it.)
Dave
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