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

On Mon, May 24, 2010 at 10:26:43AM -0400, Cole Robinson wrote: > 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(a)redhat.com&gt; >>> --- >>> 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. I'd really recommend against telling people to configure libvirt to run the guests as their own $USER because that'll open a huge can of worms.

Better to tell them to add an ACL to /dev/snd/* using setfacl to add the qemu user to the ACL for the sound card, or drop in a udev rule todo the same.