Re: [PATCH v4 3/3] PCI/AER: Clear UNCOR_STATUS bits that might be ANFE

[Kuppuswamy, Sathyanarayanan]

On 5/9/24 1:48 AM, Zhenzhong Duan wrote:
> When processing an ANFE, ideally both correctable error(CE) status and
> uncorrectable error(UE) status should be cleared. However, there is no
> way to fully identify the UE associated with ANFE. Even worse, Non-Fatal
> Error(NFE) may set the same UE status bit as ANFE. Treating an ANFE as
> NFE will bring some issues, i.e., breaking softwore probing; treating
/s/softwore/software

May be this is already discussed. But can you explain why treating
AFNE as non-fatal error will bring probing issues?
> NFE as ANFE will make us ignoring some UEs which need active recover
/s/ignoring/ignore
> operation. To avoid clearing UEs that are not ANFE by accident, the
> most conservative route is taken here: If any of the NFE Detected bits
> is set in Device Status, do not touch UE status, they should be cleared
> later by the UE handler. Otherwise, a specific set of UEs that may be
> raised as ANFE according to the PCIe specification will be cleared if
> their corresponding severity is Non-Fatal.
>
> For instance, previously when kernel receives an ANFE with Poisoned TLP
> in OS native AER mode, only status of CE will be reported and cleared:
>
>   AER: Correctable error message received from 0000:b7:02.0
>   PCIe Bus Error: severity=Correctable, type=Transaction Layer, (Receiver ID)
>     device [8086:0db0] error status/mask=00002000/00000000
>      [13] NonFatalErr
>
> If the kernel receives a Malformed TLP after that, two UEs will be
> reported, which is unexpected. Malformed TLP Header is lost since
> the previous ANFE gated the TLP header logs:
>
>   PCIe Bus Error: severity="Uncorrectable (Fatal), type=Transaction Layer, (Receiver ID)
>     device [8086:0db0] error status/mask=00041000/00180020
>      [12] TLP                    (First)
>      [18] MalfTLP
>
> Now, for the same scenario, both CE status and related UE status will be
> reported and cleared after ANFE:
>
>   AER: Correctable error message received from 0000:b7:02.0
>   PCIe Bus Error: severity=Correctable, type=Transaction Layer, (Receiver ID)
>     device [8086:0db0] error status/mask=00002000/00000000
>      [13] NonFatalErr
>     Uncorrectable errors that may cause Advisory Non-Fatal:
>      [18] TLP
>
> Tested-by: Yudong Wang <yudong.wang@xxxxxxxxx>
> Co-developed-by: "Wang, Qingshun" <qingshun.wang@xxxxxxxxxxxxxxx>
> Signed-off-by: "Wang, Qingshun" <qingshun.wang@xxxxxxxxxxxxxxx>
> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@xxxxxxxxx>
> ---
>  drivers/pci/pcie/aer.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
> index ed435f09ac27..6a6a3a40569a 100644
> --- a/drivers/pci/pcie/aer.c
> +++ b/drivers/pci/pcie/aer.c
> @@ -1115,9 +1115,14 @@ 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)
> +		if (aer) {
>  			pci_write_config_dword(dev, aer + PCI_ERR_COR_STATUS,
>  					info->status);
> +			if (info->anfe_status)
> +				pci_write_config_dword(dev,
> +						       aer + PCI_ERR_UNCOR_STATUS,
> +						       info->anfe_status);
> +		}

Why split the handling part and storing part into two patches? Why not merge
this part of patch 1/3.

>  		if (pcie_aer_is_native(dev)) {
>  			struct pci_driver *pdrv = dev->driver;
>  

-- 
Sathyanarayanan Kuppuswamy
Linux Kernel Developer