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 Tue, Jan 17, 2023 at 03:33:42PM +0100, Takashi Iwai wrote:
> On Tue, 17 Jan 2023 15:21:23 +0100,
> Marek Marczykowski-Górecki wrote:
> > 
> > On Tue, Jan 17, 2023 at 12:36:28PM +0100, Marek Marczykowski-Górecki wrote:
> > > On Tue, Jan 17, 2023 at 08:58:57AM +0100, Takashi Iwai wrote:
> > > > On Mon, 16 Jan 2023 16:55:11 +0100,
> > > > Takashi Iwai wrote:
> > > > > 
> > > > > On Tue, 27 Dec 2022 16:26:54 +0100,
> > > > > Marek Marczykowski-Górecki wrote:
> > > > > > 
> > > > > > 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.
> > > > > 
> > > > > Then we seem to go back again with the coherent memory allocation for
> > > > > the fallback sg cases.  It was changed because the use of
> > > > > dma_alloc_coherent() caused a problem with IOMMU case for retrieving
> > > > > the page addresses, but since the commit 9736a325137b, we essentially
> > > > > avoid the fallback when IOMMU is used, so it should be fine again.
> > > > > 
> > > > > Let me know if the patch like below works for you instead of the
> > > > > previous hack to disable SG-buffer (note: totally untested!)
> > > > 
> > > > Gah, there was an obvious typo, scratch that.
> > > > 
> > > > Below is a proper patch.  Please try this one instead.
> > > 
> > > Thanks, I'll give it a try.
> > 
> > Unfortunately, it doesn't help, it stopped working again, after about 3h
> > uptime.
> 
> Aha, then it might be rather other way round;
> dma_alloc_noncontiguous() doesn't work on Xen properly.
> 
> Could you try the one below instead of the previous?

Unfortunately, this one doesn't fix it either :/

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

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