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