Re: [RFC PATCH] PCI: Extend D3hot delay for NVIDIA HDA controllers

Alex Williamson
2023-04-06T22:02:14Z

On Thu, 6 Apr 2023 16:50:49 -0500
Bjorn Helgaas <helgaas@kernel.org> wrote:

> [+cc Sajid, author of 3e347969a577]
>
> On Tue, Mar 28, 2023 at 04:59:30PM -0600, Alex Williamson wrote:
> > Assignment of NVIDIA Ampere-based GPUs have seen a regression since the
> > below referenced commit, where the reduced D3hot transition delay appears
> > to introduce a small window where a D3hot->D0 transition followed by a bus
> > reset can wedge the device. The entire device is subsequently unavailable,
> > returning -1 on config space read and is unrecoverable without a host reset.
> >
> > This has been observed with RTX A2000 and A5000 GPU and audio functions
> > assigned to a Windows VM, where shutdown of the VM places the devices in
> > D3hot prior to vfio-pci performing a bus reset when userspace releases the
> > devices. The issue has roughly a 2-3% chance of occurring per shutdown.
> >
> > Restoring the HDA controller d3hot_delay to the effective value before the
> > below commit has been shown to resolve the issue.
>
> Interesting. This sounds like it was a hassle to track down. I guess
> we knew there was some risk in reducing those delays.
>
> Did you by chance notice whether the actual delay when the device gets
> wedged is sufficient per spec?
>
> If there's a case where the usleep_range() doesn't quite wait the
> spec-mandated time, we should adjust that in case we have the same
> problem with other devices.

That would have been a good test, unfortunately I didn't check and
don't currently have access to the system anymore. Perhaps this is
something the NVIDIA folks can check as they're investigating the scope
of affected hardware. Thanks,

Alex

> > I'm looking for input from NVIDIA whether this issue is unique to
> > Ampere-based HDA controllers or should be assumed to linger in both older
> > and newer controllers as well. Currently we've not been able to reproduce
> > the issue other than on Ampere HDA controllers, however the implementation
> > here includes all NVIDIA HDA controllers based on PCI vendor and device
> > class.
> >
> > If we were to limit the quirk to Ampere HDA controllers, I think that would
> > include:
> >
> > 1aef GA102 High Definition Audio Controller
> > 228b GA104 High Definition Audio Controller
> > 228e GA106 High Definition Audio Controller
> >
> > Cc: Abhishek Sahu <abhsahu@nvidia.com>
> > Cc: Tarun Gupta <targupta@nvidia.com>
> > Fixes: 3e347969a577 ("PCI/PM: Reduce D3hot delay with usleep_range()")
> > Reported-by: Zhiyi Guo <zhguo@redhat.com>
> > Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
> > ---
> > drivers/pci/quirks.c | 13 +++++++++++++
> > 1 file changed, 13 insertions(+)
> >
> > diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> > index 44cab813bf95..f4e2a88729fd 100644
> > --- a/drivers/pci/quirks.c
> > +++ b/drivers/pci/quirks.c
> > @@ -1939,6 +1939,19 @@ static void quirk_radeon_pm(struct pci_dev *dev)
> > }
> > DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_ATI, 0x6741, quirk_radeon_pm);
> >
> > +/*
> > + * NVIDIA Ampere-based HDA controllers can wedge the whole device if a bus
> > + * reset is performed too soon after transition to D0, extend d3hot_delay
> > + * to previous effective default for all NVIDIA HDA controllers.
> > + */
> > +static void quirk_nvidia_hda_pm(struct pci_dev *dev)
> > +{
> > + quirk_d3hot_delay(dev, 20);
> > +}
> > +DECLARE_PCI_FIXUP_CLASS_FINAL(PCI_VENDOR_ID_NVIDIA, PCI_ANY_ID,
> > + PCI_CLASS_MULTIMEDIA_HD_AUDIO, 8,
> > + quirk_nvidia_hda_pm);
> > +
> > /*
> > * Ryzen5/7 XHCI controllers fail upon resume from runtime suspend or s2idle.
> > * https://bugzilla.kernel.org/show_bug.cgi?id=205587
> >
> >
>