[libvirt] [PATCH] qemu: Allow using regular audio backends with VNC

[Cole Robinson]

On 05/24/2010 10:14 AM, Daniel P. Berrange wrote:
> On Thu, May 20, 2010 at 12:04:04PM -0400, Cole Robinson wrote:
>> Currently all host audio backends are disabled if a VM is using VNC, in
>> favor of the QEMU VNC audio extension. Unfortunately no released VNC
>> client supports this extension, so users have no way of getting audio
>> to work if using VNC.
>>
>> Add a new config option in qemu.conf which allows changing libvirt's
>> behavior, but keep the default intact.
>>
>> Signed-off-by: Cole Robinson <crobinso at redhat.com>
>> ---
>>  src/qemu/qemu.conf   |   10 ++++++++++
>>  src/qemu/qemu_conf.c |   17 ++++++++++++-----
>>  src/qemu/qemu_conf.h |    2 ++
>>  3 files changed, 24 insertions(+), 5 deletions(-)
>>
>> diff --git a/src/qemu/qemu.conf b/src/qemu/qemu.conf
>> index 3da332f..fec946d 100644
>> --- a/src/qemu/qemu.conf
>> +++ b/src/qemu/qemu.conf
>> @@ -168,3 +168,13 @@
>>  # be assigned to guests.
>>  #
>>  # relaxed_acs_check = 1
>> +
>> +
>> +# QEMU implements anextension for providing audio over a VNC connection,
>> +# though if your VNC client does not support it, your only chance for getting
>> +# sound output is through regular audio backends. By default, libvirt will
>> +# disable all QEMU sound backends if using VNC, since they can cause
>> +# permissions issues. Enabling this option will make libvirtd honor the
>> +# QEMU_AUDIO_DRV environment variable when using VNC.
>> +#
>> +# vnc_enable_audio_backend = 0
> 
> I think this would be better named as 'vnc_allow_host_audio'
> since its not toggling VNC audio, just whether it is allowed
> to use the host audio drivers. 
> 

Okay, I'll change and resend.

> NB, even with this toggled things are unlikely to magically
> 'just work'. If QEMU is running as 'qemu' user ID, that user
> won't have any permissions to use /dev/snd/* devices. And
> if running as 'root' then pulseaudio won't autospawn so will
> need to be run manually.
> 

Right. Currently getting sound to work in Fedora is a big pain, and
there have been quite a few user complaints. I'm going to write up a
'known bug' page, documenting a workaround of qemu.conf user/group =
$USER to fix the issue, but this patch will still need to be backported.

- Cole