Re: Intel HD Audio: sound stops working in Xen PV dom0 in >=5.17

["Marek Marczykowski-Górecki" <marmarek@invisiblethingslab.com>]

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On Fri, Dec 09, 2022 at 01:40:15PM +0100, Marek Marczykowski-Górecki wrote:
> On Fri, Dec 09, 2022 at 09:10:19AM +0100, Takashi Iwai wrote:
> > On Fri, 09 Dec 2022 02:27:30 +0100,
> > Marek Marczykowski-Górecki wrote:
> > > 
> > > Hi,
> > > 
> > > Under Xen PV dom0, with Linux >= 5.17, sound stops working after few
> > > hours. pavucontrol still shows meter bars moving, but the speakers
> > > remain silent. At least on some occasions I see the following message in
> > > dmesg:
> > > 
> > >   [ 2142.484553] snd_hda_intel 0000:00:1f.3: Unstable LPIB (18144 >= 6396); disabling LPIB delay counting

Hit the issue again, this message did not appear in the log (or at least
not yet).

(...)

> > In anyway, please check the behavior with 6.1-rc8 + the commit
> > cc26516374065a34e10c9a8bf3e940e42cd96e2a
> >     ALSA: memalloc: Allocate more contiguous pages for fallback case
> > from for-next of my sound git tree (which will be in 6.2-rc1).

This did not helped.

> Looking at the mentioned commits, there is one specific aspect of Xen PV
> that may be relevant. It configures PAT differently than native Linux.
> Theoretically Linux adapts automatically and using proper API (like
> set_memory_wc()) should just work, but at least for i915 driver it
> causes issues (not fully tracked down yet). Details about that bug
> report include some more background:
> https://lore.kernel.org/intel-gfx/Y5Hst0bCxQDTN7lK@mail-itl/
> 
> Anyway, I have tested it on a Xen modified to setup PAT the same way as
> native Linux and the audio issue is still there.
> 
> > If the problem persists, another thing to check is the hack below
> > works.

Trying this one now.

> > -- 8< --
> > --- a/sound/pci/hda/hda_intel.c
> > +++ b/sound/pci/hda/hda_intel.c
> > @@ -1808,9 +1808,16 @@ static int azx_create(struct snd_card *card, struct pci_dev *pci,
> >  	if (err < 0)
> >  		return err;
> >  
> > +#if 0
> >  	/* use the non-cached pages in non-snoop mode */
> >  	if (!azx_snoop(chip))
> >  		azx_bus(chip)->dma_type = SNDRV_DMA_TYPE_DEV_WC_SG;
> > +#else
> > +	if (!azx_snoop(chip))
> > +		azx_bus(chip)->dma_type = SNDRV_DMA_TYPE_DEV_SG;
> > +	else
> > +		azx_bus(chip)->dma_type = SNDRV_DMA_TYPE_DEV;
> > +#endif
> >  
> >  	if (chip->driver_type == AZX_DRIVER_NVIDIA) {
> >  		dev_dbg(chip->card->dev, "Enable delay in RIRB handling\n");

-- 
Best Regards,
Marek Marczykowski-Górecki
Invisible Things Lab

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