Re: [Qemu-devel] Wierd hack to sound/pci/intel8x0.c

[Takashi Iwai]

At Mon, 07 Nov 2011 10:25:24 +0100,
Gerd Hoffmann wrote:
> 
>   Hi,
> 
> > Agreed.  If we can know the virtual device for KVM in a better way
> > (e.g. any specific PCI SSID or such), we can narrow the condition more
> > safely.
> 
> PCI Subsystem ID 1af4:1100 is qemu/kvm (not only Intel HDA, most other
> emulated pci devices have it too). Complete entry:
> 
> 00:04.0 0403: 8086:2668 (rev 01)
>         Subsystem: 1af4:1100
>         Physical Slot: 4
>         Flags: bus master, fast devsel, latency 0, IRQ 11
>         Memory at e2030000 (32-bit, non-prefetchable) [size=16K]
>         Kernel driver in use: HDA Intel
>         Kernel modules: snd-hda-intel

Thanks.

BTW, this reminds me of a possible improvement in the current HD-audio
driver.  It has some workaround for the delayed DMA-position update
(the DMA-position isn't completely updated when IRQ is issued) by
offsetting the buffer position.  This is controlled by bdl_pos_adj
option of snd-hda-intel driver, and this could be zero for VMs.


Takashi