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xen-users
RE: [Xen-users] Re: XEN sound emulation locks device exclusively
> -----Original Message-----
> From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx
> [mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of
> Csillag, Kristof (GE Healthcare, consultant)
> Sent: 13 November 2006 07:42
> To: xen-users@xxxxxxxxxxxxxxxxxxx
> Subject: [Xen-users] Re: XEN sound emulation locks device exclusively
>
> > As I think XEN has no "audio emulation", there's probably
> no fix other than
> > using VMware that has an audio emulation.
>
> OK, so I have the wrong idea about how XEN handles sound.
> (I found no documentation on this, so it was basically a guess.)
>
> Here is what I know:
>
> - In the notebook computer there is and Intel HDA sound card.
> - In the configuration file for my HVM guest, I have "soundhw='sb16'".
> - The WinXP running as HVM guest sees a Sound Blaster 16
> sound device, and can use it.
>
> Here is what I thought:
>
> - Either the XEN hypervisor, or some user-space tool
> (probably the later) emulates
> the hardware interface of a SB16 for the HVM host, and
> - it relays the sound to the sound system of DOM0.
>
> If this is not how it goes, then what?
> I thought that since there is no real SB16 in the host in question,
> the SB16 interface must have been emulated,
> but from what you say I seem to be mistaken.
>
> Could someone please explain this, or give a link to the
> appropriate documentation?
If it's a HVM guest, the sound emulation is done in QEMU-DM, the device
model for the HVM mode.
In fact, qemu-dm is responsible for ALL hardware emulation with a few
exceptions (timer and interrupt controller functionality) that for
performance reasons are in Xen itself.
So, yes, qemu-dm will have a SB16 type emulation layer that then
forwards the sound to be played to the real hardware.
I would expect that this happens at a very low level, so it's "bare
samples" being sent to the hardware, which may mean that it needs to
lock the device exclusively to prevent other streams from interacting.
--
Mats
>
> Thank you:
>
>
> Kristof Csillag
>
> _______________________________________________
> Xen-users mailing list
> Xen-users@xxxxxxxxxxxxxxxxxxx
> http://lists.xensource.com/xen-users
>
>
>
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