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Date:   Thu, 27 Jan 2022 15:01:25 +0800
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Cc:     baolu.lu@linux.intel.com, mika.westerberg@linux.intel.com,
        koba.ko@canonical.com, Russell Currey <ruscur@russell.cc>,
        Oliver O'Halloran <oohall@gmail.com>,
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To:     Kai-Heng Feng <kai.heng.feng@canonical.com>, bhelgaas@google.com
References: <20220127025418.1989642-1-kai.heng.feng@canonical.com>
From:   Lu Baolu <baolu.lu@linux.intel.com>
Subject: Re: [PATCH v2 1/2] PCI/AER: Disable AER service when link is in L2/L3
 ready, L2 and L3 state
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On 2022/1/27 10:54, 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
> S3:
> [   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.
> 
> There's another case, when Thunderbolt reaches D3cold:
> [   30.100211] pcieport 0000:00:1d.0: AER: Uncorrected (Non-Fatal) error received: 0000:00:1d.0
> [   30.100251] pcieport 0000:00:1d.0: PCIe Bus Error: severity=Uncorrected (Non-Fatal), type=Transaction Layer, (Requester ID)
> [   30.100256] pcieport 0000:00:1d.0:   device [8086:7ab0] error status/mask=00100000/00004000
> [   30.100262] pcieport 0000:00:1d.0:    [20] UnsupReq               (First)
> [   30.100267] pcieport 0000:00:1d.0: AER:   TLP Header: 34000000 08000052 00000000 00000000
> [   30.100372] thunderbolt 0000:0a:00.0: AER: can't recover (no error_detected callback)
> [   30.100401] xhci_hcd 0000:3e:00.0: AER: can't recover (no error_detected callback)
> [   30.100427] pcieport 0000:00:1d.0: AER: device recovery failed
> 
> So disable AER service to avoid the noises from turning power rails
> on/off when the device is in low power states (D3hot and D3cold), as
> PCIe spec "5.2 Link State Power Management" states that TLP and DLLP
> transmission is disabled for a Link in L2/L3 Ready (D3hot), L2 (D3cold
> with aux power) and L3 (D3cold).
> 
> Bugzilla:https://bugzilla.kernel.org/show_bug.cgi?id=209149
> Bugzilla:https://bugzilla.kernel.org/show_bug.cgi?id=215453
> Fixes: 50310600ebda ("iommu/vt-d: Enable PCI ACS for platform opt in hint")

I don't know what this fix has to do with the commit 50310600ebda.
Commit 50310600ebda only makes sure that PCI ACS is enabled whenever
Intel IOMMU is on. Before this commit, PCI ACS could also be enabled
and result in the same problem. Or anything I missed?

Best regards,
baolu