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 <20210204232758.GA125392@bjorn-Precision-5520>
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From:   Kai-Heng Feng <kai.heng.feng@canonical.com>
Date:   Fri, 5 Feb 2021 23:17:32 +0800
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Subject: Re: [PATCH 1/2] PCI/AER: Disable AER interrupt during suspend
To:     Bjorn Helgaas <helgaas@kernel.org>
Cc:     Bjorn Helgaas <bhelgaas@google.com>,
        Russell Currey <ruscur@russell.cc>,
        "Oliver O'Halloran" <oohall@gmail.com>,
        Mika Westerberg <mika.westerberg@linux.intel.com>,
        Lalithambika Krishnakumar <lalithambika.krishnakumar@intel.com>,
        Lu Baolu <baolu.lu@linux.intel.com>,
        Joerg Roedel <jroedel@suse.de>,
        Alex Williamson <alex.williamson@redhat.com>,
        "open list:PCI ENHANCED ERROR HANDLING (EEH) FOR POWERPC" 
        <linuxppc-dev@lists.ozlabs.org>,
        "open list:PCI SUBSYSTEM" <linux-pci@vger.kernel.org>,
        open list <linux-kernel@vger.kernel.org>
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On Fri, Feb 5, 2021 at 7:28 AM Bjorn Helgaas <helgaas@kernel.org> wrote:
>
> [+cc Alex]
>
> On Thu, Jan 28, 2021 at 12:09:37PM +0800, Kai-Heng Feng wrote:
> > On Thu, Jan 28, 2021 at 4:51 AM Bjorn Helgaas <helgaas@kernel.org> wrote:
> > > On Thu, Jan 28, 2021 at 01:31:00AM +0800, Kai-Heng Feng wrote:
> > > > Commit 50310600ebda ("iommu/vt-d: Enable PCI ACS for platform opt in
> > > > hint") enables ACS, and some platforms lose its NVMe after resume from
> > > > firmware:
> > > > [   50.947816] pcieport 0000:00:1b.0: DPC: containment event, status:0x1f01 source:0x0000
> > > > [   50.947817] pcieport 0000:00:1b.0: DPC: unmasked uncorrectable error detected
> > > > [   50.947829] pcieport 0000:00:1b.0: PCIe Bus Error: severity=Uncorrected (Non-Fatal), type=Transaction Layer, (Receiver ID)
> > > > [   50.947830] pcieport 0000:00:1b.0:   device [8086:06ac] error status/mask=00200000/00010000
> > > > [   50.947831] pcieport 0000:00:1b.0:    [21] ACSViol                (First)
> > > > [   50.947841] pcieport 0000:00:1b.0: AER: broadcast error_detected message
> > > > [   50.947843] nvme nvme0: frozen state error detected, reset controller
> > > >
> > > > It happens right after ACS gets enabled during resume.
> > > >
> > > > To prevent that from happening, disable AER interrupt and enable it on
> > > > system suspend and resume, respectively.
> > >
> > > Lots of questions here.  Maybe this is what we'll end up doing, but I
> > > am curious about why the error is reported in the first place.
> > >
> > > Is this a consequence of the link going down and back up?
> >
> > Could be. From the observations, it only happens when firmware suspend
> > (S3) is used.
> > Maybe it happens when it's gets powered up, but I don't have equipment
> > to debug at hardware level.
> >
> > If we use non-firmware suspend method, enabling ACS after resume won't
> > trip AER and DPC.
> >
> > > Is it consequence of the device doing a DMA when it shouldn't?
> >
> > If it's doing DMA while suspending, the same error should also happen
> > after NVMe is suspended and before PCIe port suspending.
> > Furthermore, if non-firmware suspend method is used, there's so such
> > issue, so less likely to be any DMA operation.
> >
> > > Are we doing something in the wrong order during suspend?  Or maybe
> > > resume, since I assume the error is reported during resume?
> >
> > Yes the error is reported during resume. The suspend/resume order
> > seems fine as non-firmware suspend doesn't have this issue.
>
> I really feel like we need a better understanding of what's going on
> here.  Disabling the AER interrupt is like closing our eyes and
> pretending that because we don't see it, it didn't happen.
>
> An ACS error is triggered by a DMA, right?  I'm assuming an MMIO
> access from the CPU wouldn't trigger this error.  And it sounds like
> the error is triggered before we even start running the driver after
> resume.
>
> If we're powering up an NVMe device from D3cold and it DMAs before the
> driver touches it, something would be seriously broken.  I doubt
> that's what's happening.  Maybe a device could resume some previously
> programmed DMA after powering up from D3hot.

I am not that familiar with PCIe ACS/AER/DPC, so I can't really answer
questions you raised.
PCIe spec doesn't say the suspend/resume order is also not helping here.

However, I really think it's a system firmware issue.
I've seen some suspend-to-idle platforms with NVMe can reach D3cold,
those are unaffected.

>
> Or maybe the error occurred on suspend, like if the device wasn't
> quiesced or something, but we didn't notice it until resume?  The
> AER error status bits are RW1CS, which means they can be preserved
> across hot/warm/cold resets.
>
> Can you instrument the code to see whether the AER error status bit is
> set before enabling ACS?  I'm not sure that merely enabling ACS (I
> assume you mean pci_std_enable_acs(), where we write PCI_ACS_CTRL)
> should cause an interrupt for a previously-logged error.  I suspect
> that could happen when enabling *AER*, but I wouldn't think it would
> happen when enabling *ACS*.

Diff to print AER status:
https://bugzilla.kernel.org/show_bug.cgi?id=209149#c11

And dmesg:
https://bugzilla.kernel.org/show_bug.cgi?id=209149#c12

Looks like the read before suspend and after resume are both fine.

>
> Does this error happen on multiple machines from different vendors?
> Wondering if it could be a BIOS issue, e.g., BIOS not cleaning up
> after it did something to cause an error.

AFAIK, systems from both HP and Dell are affected.
I was told that the reference platform from Intel is using
suspend-to-idle, but vendors changed the sleep method to S3 to have
lower power consumption to pass regulation.

Kai-Heng

>
> > > If we *do* take the error, why doesn't DPC recovery work?
> >
> > It works for the root port, but not for the NVMe drive:
> > [   50.947816] pcieport 0000:00:1b.0: DPC: containment event,
> > status:0x1f01 source:0x0000
> > [   50.947817] pcieport 0000:00:1b.0: DPC: unmasked uncorrectable error detected
> > [   50.947829] pcieport 0000:00:1b.0: PCIe Bus Error:
> > severity=Uncorrected (Non-Fatal), type=Transaction Layer, (Receiver
> > ID)
> > [   50.947830] pcieport 0000:00:1b.0:   device [8086:06ac] error
> > status/mask=00200000/00010000
> > [   50.947831] pcieport 0000:00:1b.0:    [21] ACSViol                (First)
> > [   50.947841] pcieport 0000:00:1b.0: AER: broadcast error_detected message
> > [   50.947843] nvme nvme0: frozen state error detected, reset controller
> > [   50.948400] ACPI: EC: event unblocked
> > [   50.948432] xhci_hcd 0000:00:14.0: PME# disabled
> > [   50.948444] xhci_hcd 0000:00:14.0: enabling bus mastering
> > [   50.949056] pcieport 0000:00:1b.0: PME# disabled
> > [   50.949068] pcieport 0000:00:1c.0: PME# disabled
> > [   50.949416] e1000e 0000:00:1f.6: PME# disabled
> > [   50.949463] e1000e 0000:00:1f.6: enabling bus mastering
> > [   50.951606] sd 0:0:0:0: [sda] Starting disk
> > [   50.951610] nvme 0000:01:00.0: can't change power state from D3hot
> > to D0 (config space inaccessible)
> > [   50.951730] nvme nvme0: Removing after probe failure status: -19
> > [   50.952360] nvme nvme0: failed to set APST feature (-19)
> > [   50.971136] snd_hda_intel 0000:00:1f.3: PME# disabled
> > [   51.089330] pcieport 0000:00:1b.0: AER: broadcast resume message
> > [   51.089345] pcieport 0000:00:1b.0: AER: device recovery successful
> >
> > But I think why recovery doesn't work for NVMe is for another discussion...
> >
> > Kai-Heng
> >
> > >
> > > > Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=209149
> > > > Fixes: 50310600ebda ("iommu/vt-d: Enable PCI ACS for platform opt in hint")
> > > > Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
> > > > ---
> > > >  drivers/pci/pcie/aer.c | 18 ++++++++++++++++++
> > > >  1 file changed, 18 insertions(+)
> > > >
> > > > diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
> > > > index 77b0f2c45bc0..0e9a85530ae6 100644
> > > > --- a/drivers/pci/pcie/aer.c
> > > > +++ b/drivers/pci/pcie/aer.c
> > > > @@ -1365,6 +1365,22 @@ static int aer_probe(struct pcie_device *dev)
> > > >       return 0;
> > > >  }
> > > >
> > > > +static int aer_suspend(struct pcie_device *dev)
> > > > +{
> > > > +     struct aer_rpc *rpc = get_service_data(dev);
> > > > +
> > > > +     aer_disable_rootport(rpc);
> > > > +     return 0;
> > > > +}
> > > > +
> > > > +static int aer_resume(struct pcie_device *dev)
> > > > +{
> > > > +     struct aer_rpc *rpc = get_service_data(dev);
> > > > +
> > > > +     aer_enable_rootport(rpc);
> > > > +     return 0;
> > > > +}
> > > > +
> > > >  /**
> > > >   * aer_root_reset - reset Root Port hierarchy, RCEC, or RCiEP
> > > >   * @dev: pointer to Root Port, RCEC, or RCiEP
> > > > @@ -1437,6 +1453,8 @@ static struct pcie_port_service_driver aerdriver = {
> > > >       .service        = PCIE_PORT_SERVICE_AER,
> > > >
> > > >       .probe          = aer_probe,
> > > > +     .suspend        = aer_suspend,
> > > > +     .resume         = aer_resume,
> > > >       .remove         = aer_remove,
> > > >  };
> > > >
> > > > --
> > > > 2.29.2
> > > >