Re: [RFC PATCH 2/9] PCI/AER: Call AER CE handler before clearing AER CE status register

Terry Bowman
2024-06-24T15:08:50Z

On 6/20/24 06:31, Jonathan Cameron wrote:
> On Mon, 17 Jun 2024 15:04:04 -0500
> Terry Bowman <terry.bowman@amd.com> wrote:
>
>> The AER service driver clears the AER correctable error (CE) status before
>> calling the correctable error handler. This results in the error's status
>> not correctly reflected if read from the CE handler.
>>
>> The AER CE status is needed by the portdrv's CE handler. The portdrv's
>> CE handler is intended to only call the registered notifier callbacks
>> if the CE error status has correctable internal error (CIE) set.
>>
>> This is not a problem for AER uncorrrectbale errors (UCE). The UCE status
>
> uncorrectable
>

Thank you.

>> is still present in the AER capability and available for reading, if
>> needed, when the UCE handler is called.
>
> I'm seeing the clear in the DPC path for UCE. For other cases is
> it a side effect of the reset?
>

Depends on when its being read. I'm assuming this is after recovery in your case.
And after recovery it will be zeroed.

Regards,
Terry

>>
>> Change the order of clearing the CE status and calling the CE handler.
>> Make it to call the CE handler first and then clear the CE status
>> after returning.
>>
>> Signed-off-by: Terry Bowman <terry.bowman@amd.com>
>> Cc: Bjorn Helgaas <bhelgaas@google.com>
>> Cc: linux-pci@vger.kernel.org
> Seems reasonable, but many gremlins around the ordering in these
> flows, so I'm to particularly confident. With that in mind.
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huwei.com>
>
>> ---
>> drivers/pci/pcie/aer.c | 7 ++++---
>> 1 file changed, 4 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
>> index ac6293c24976..4dc03cb9aff0 100644
>> --- a/drivers/pci/pcie/aer.c
>> +++ b/drivers/pci/pcie/aer.c
>> @@ -1094,9 +1094,6 @@ static void pci_aer_handle_error(struct pci_dev *dev, struct aer_err_info *info)
>> * Correctable error does not need software intervention.
>> * No need to go through error recovery process.
>> */
>> - if (aer)
>> - pci_write_config_dword(dev, aer + PCI_ERR_COR_STATUS,
>> - info->status);
>> if (pcie_aer_is_native(dev)) {
>> struct pci_driver *pdrv = dev->driver;
>>
>> @@ -1105,6 +1102,10 @@ static void pci_aer_handle_error(struct pci_dev *dev, struct aer_err_info *info)
>> pdrv->err_handler->cor_error_detected(dev);
>> pcie_clear_device_status(dev);
>> }
>> + if (aer)
>> + pci_write_config_dword(dev, aer + PCI_ERR_COR_STATUS,
>> + info->status);
>> +
>> } else if (info->severity == AER_NONFATAL)
>> pcie_do_recovery(dev, pci_channel_io_normal, aer_root_reset);
>> else if (info->severity == AER_FATAL)
>