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Re: [libvirt] [PATCH] Allow control over QEMU audio backend



On Tue, Sep 22, 2009 at 11:45:02AM +0100, Daniel P. Berrange wrote:
> When using VNC for graphics + keyboard + mouse, we shouldn't
> then use the host OS for audio. Audio should go back over
> VNC.
> 
> When using SDL for graphics, we should use the host OS for
> audio since that's where the display is. We need to allow
> certain QEMU env variables to be passed through to guest
> too to allow choice of QEMU audio backend.

 All this makes sense !

> * qemud/libvirtd.sysconf: Mention QEMU/SDL audio env vars
> * src/qemu_conf.c: Passthrough QEMU/SDL audio env for SDL display,
>   disable host audio for VNC display
> ---
>  daemon/libvirtd.sysconf |    8 ++++++++
>  src/qemu/qemu_conf.c    |   14 ++++++++++++++
>  2 files changed, 22 insertions(+), 0 deletions(-)
> 
> diff --git a/daemon/libvirtd.sysconf b/daemon/libvirtd.sysconf
> index fe4596a..28080a0 100644
> --- a/daemon/libvirtd.sysconf
> +++ b/daemon/libvirtd.sysconf
> @@ -7,3 +7,11 @@
>  
>  # Override Kerberos service keytab for SASL/GSSAPI
>  #KRB5_KTNAME=/etc/libvirt/krb5.tab
> +
> +# Override the QEMU/SDL default audio driver probing when
> +# starting virtual machines using SDL graphics
> +#
> +# NB these have no effect for VMs using VNC
> +#QEMU_AUDIO_DRV=sdl
> +#
> +#SDL_AUDIODRIVER=pulse
> diff --git a/src/qemu/qemu_conf.c b/src/qemu/qemu_conf.c
> index 273aeca..74ca52b 100644
> --- a/src/qemu/qemu_conf.c
> +++ b/src/qemu/qemu_conf.c
> @@ -2109,6 +2109,13 @@ int qemudBuildCommandLine(virConnectPtr conn,
>              ADD_ARG_LIT("-k");
>              ADD_ARG_LIT(def->graphics[0]->data.vnc.keymap);
>          }
> +
> +        /* QEMU implements a VNC extension for providing audio, so we
> +         * set the audio backend to none, to prevent it opening the
> +         * host OS audio devices since that causes security issues
> +         * and is non-sensical when using VNC.
> +         */
> +        ADD_ENV_LIT("QEMU_AUDIO_DRV=none");
>      } else if ((def->ngraphics == 1) &&
>                 def->graphics[0]->type == VIR_DOMAIN_GRAPHICS_TYPE_SDL) {
>          char *xauth = NULL;
> @@ -2131,6 +2138,13 @@ int qemudBuildCommandLine(virConnectPtr conn,
>              ADD_ENV(display);
>          if (def->graphics[0]->data.sdl.fullscreen)
>              ADD_ARG_LIT("-full-screen");
> +
> +        /* If using SDL for video, then we should just let it
> +         * use QEMU's host audio drivers, possibly SDL too
> +         * User can set these two before starting libvirtd
> +         */
> +        ADD_ENV_COPY("QEMU_AUDIO_DRV");
> +        ADD_ENV_COPY("SDL_AUDIODRIVER");
>      }
>  
>      if (def->nvideos) {

 ACK,

I wonder if that would be sufficient to drop the
libvirt-0.6.4-svirt-sound.patch that we carry in Fedora, not sure
because we still may use the local audio in some cases. Opinion ?

Daniel

-- 
Daniel Veillard      | libxml Gnome XML XSLT toolkit  http://xmlsoft.org/
daniel veillard com  | Rpmfind RPM search engine http://rpmfind.net/
http://veillard.com/ | virtualization library  http://libvirt.org/


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