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    SubjectRe: [PATCH v3 8/9] PCI/ERR: Clear fatal error status when pci_channel_io_frozen
    Hi Zhuo,

    On Wed, Sep 28, 2022 at 06:59:45PM +0800, Zhuo Chen wrote:
    > When state is pci_channel_io_frozen in pcie_do_recovery(), the
    > severity is fatal and fatal error status should be cleared.
    > So add pci_aer_clear_fatal_status().
    >
    > Signed-off-by: Zhuo Chen <chenzhuo.1@bytedance.com>
    > ---
    > drivers/pci/pcie/err.c | 5 ++++-
    > 1 file changed, 4 insertions(+), 1 deletion(-)
    >
    > diff --git a/drivers/pci/pcie/err.c b/drivers/pci/pcie/err.c
    > index f80b21244ef1..b46f1d36c090 100644
    > --- a/drivers/pci/pcie/err.c
    > +++ b/drivers/pci/pcie/err.c
    > @@ -241,7 +241,10 @@ pci_ers_result_t pcie_do_recovery(struct pci_dev *dev,
    > pci_walk_bridge(bridge, report_resume, &status);
    >
    > pcie_clear_device_status(dev);
    > - pci_aer_clear_nonfatal_status(dev);
    > + if (state == pci_channel_io_frozen)
    > + pci_aer_clear_fatal_status(dev);
    > + else
    > + pci_aer_clear_nonfatal_status(dev);

    I'm confused. It seems like we certainly need to clear fatal errors
    after they occur *somewhere*, and if we don't, surely this would be a
    very obvious issue. But you didn't mention this being a bug fix, so I
    assume it's more of a cleanup.

    If it *is* a bug fix, please say that and give a hint about what the
    bug looks like, e.g., what sort of messages a user might see.

    If it's not a bug fix, I don't understand how AER fatal errors get
    cleared today. The PCI_ERR_UNCOR_STATUS bits are sticky, so they're
    not cleared by a reset. In the current tree, these are the only
    places I see that clear AER fatal errors:

    pci_init_capabilities
    pci_aer_init # once at device enumeration
    pci_aer_clear_status
    pci_aer_raw_clear_status
    pci_write_config_dword(dev, aer + PCI_ERR_UNCOR_STATUS, status)

    aer_probe
    aer_enable_rootport # once at Root Port enumeration
    pci_write_config_dword(pdev, aer + PCI_ERR_UNCOR_STATUS, reg32)

    dpc_process_error # after DPC triggered
    pci_aer_clear_fatal_status
    pci_write_config_dword(dev, aer + PCI_ERR_UNCOR_STATUS, status)

    edr_handle_event # after EDR event
    pci_aer_raw_clear_status
    pci_write_config_dword(dev, aer + PCI_ERR_UNCOR_STATUS, status)

    pci_restore_state # after reset or PM sleep/resume
    pci_aer_clear_status
    pci_aer_raw_clear_status
    pci_write_config_dword(dev, aer + PCI_ERR_UNCOR_STATUS, status)

    The only one that could clear errors after an AER error (not DPC or
    EDR), would be the pci_restore_state() in the reset path. If the
    current code relies on that, I'd say that's a pretty non-obvious
    dependency.

    > pci_info(bridge, "device recovery successful\n");
    > return status;
    > --
    > 2.30.1 (Apple Git-130)
    >

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