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

[Marek Marczykowski-Górecki]

On Thu, Dec 22, 2022 at 09:09:15AM +0100, Takashi Iwai wrote:
> On Sat, 10 Dec 2022 17:17:42 +0100,
> Marek Marczykowski-Górecki wrote:
> > 
> > On Sat, Dec 10, 2022 at 02:00:06AM +0100, Marek Marczykowski-Górecki wrote:
> > > 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.
> > 
> > And this one didn't either :/
> 
> (Sorry for the late reply, as I've been off in the last weeks.)
> 
> I think the hack doesn't influence on the PCM buffer pages, but only
> about BDL pages.  Could you check the patch below instead?
> It'll disable the SG-buffer handling on x86 completely. 

This seems to "fix" the issue, thanks!
I guess I'll run it this way for now, but a proper solution would be
nice. Let me know if I can collect any more info that would help with
that.

> -- 8< --
> --- a/sound/core/Kconfig
> +++ b/sound/core/Kconfig
> @@ -225,8 +225,8 @@ config SND_VMASTER
>  	bool
>  
>  config SND_DMA_SGBUF
> -	def_bool y
> -	depends on X86
> +	def_bool n
> +#	depends on X86
>  
>  config SND_CTL_LED
>  	tristate

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