Re: [PATCH v2 2/4] PCI/AER: Handle Advisory Non-Fatal properly

Bjorn Helgaas
2024-02-05T23:26:18Z

In the subject, "properly" really doesn't convey information. I think
this patch does two things:

- Prints error bits that might be ANFE
- Clears UNCOR_STATUS bits that were previously not cleared

Maybe the subject line could say something about those (clearing
UNCOR_STATUS might be more important, or maybe this could even be
split into two patches so we could see both).

On Thu, Jan 25, 2024 at 02:28:00PM +0800, Wang, Qingshun wrote:
> When processing an Advisory Non-Fatal error, ideally both correctable
> error status and uncorrectable error status should be cleared. However,
> there is no way to fully identify the UE associated with ANFE. Even
> worse, a Fatal/Non-Fatal error may set the same UE status bit as ANFE.
> Assuming an ANFE is FE/NFE is kind of bad, but assuming a FE/NFE is an
> ANFE is usually unacceptable. To avoid clearing UEs that are not ANFE by
> accident, the most conservative route is taken here: If any of the
> Fatal/Non-Fatal Error 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. Additionally, log UEs that will be cleared.
>
> 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: Corrected error received: 0000:b7:02.0
> PCIe Bus Error: severity=Corrected, 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 UE will be
> reported, which is unexpected. Malformed TLP Header was lost since
> the previous ANF gated the TLP header logs:
>
> PCIe Bus Error: severity=Uncorrected (Fatal), type=Transaction Layer, (Receiver ID)
> device [8086:0db0] error status/mask=00041000/00180020
> [12] TLP (First)
> [18] MalfTLP
>
> Now, in the same scenario, both CE status and related UE status will be
> reported and cleared after ANFE:
>
> AER: Corrected error received: 0000:b7:02.0
> PCIe Bus Error: severity=Corrected, 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
>
> Signed-off-by: "Wang, Qingshun" <qingshun.wang@linux.intel.com>
> ---
> drivers/pci/pcie/aer.c | 61 +++++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 60 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
> index 6583dcf50977..713cbf625d3f 100644
> --- a/drivers/pci/pcie/aer.c
> +++ b/drivers/pci/pcie/aer.c
> @@ -107,6 +107,12 @@ struct aer_stats {
> PCI_ERR_ROOT_MULTI_COR_RCV | \
> PCI_ERR_ROOT_MULTI_UNCOR_RCV)
>
> +#define AER_ERR_ANFE_UNC_MASK (PCI_ERR_UNC_POISON_TLP | \
> + PCI_ERR_UNC_COMP_TIME | \
> + PCI_ERR_UNC_COMP_ABORT | \
> + PCI_ERR_UNC_UNX_COMP | \
> + PCI_ERR_UNC_UNSUP)
> +
> static int pcie_aer_disable;
> static pci_ers_result_t aer_root_reset(struct pci_dev *dev);
>
> @@ -612,6 +618,32 @@ const struct attribute_group aer_stats_attr_group = {
> .is_visible = aer_stats_attrs_are_visible,
> };
>
> +static int anfe_get_related_err(struct aer_err_info *info)
> +{
> + /*
> + * Take the most conservative route here. If there are
> + * Non-Fatal/Fatal errors detected, do not assume any
> + * bit in uncor_status is set by ANFE.
> + */
> + if (info->device_status & (PCI_EXP_DEVSTA_NFED | PCI_EXP_DEVSTA_FED))
> + return 0;
> + /*
> + * According to PCIe Base Specification Revision 6.1,
> + * Section 6.2.3.2.4, if an UNCOR error is rasied as
> + * Advisory Non-Fatal error, it will match the following
> + * conditions:
> + * a. The severity of the error is Non-Fatal.
> + * b. The error is one of the following:
> + * 1. Poisoned TLP
> + * 2. Completion Timeout
> + * 3. Completer Abort
> + * 4. Unexpected Completion
> + * 5. Unsupported Request
> + */
> + return info->uncor_status & ~info->uncor_mask
> + & AER_ERR_ANFE_UNC_MASK & ~info->severity;
> +}
> +
> static void pci_dev_aer_stats_incr(struct pci_dev *pdev,
> struct aer_err_info *info)
> {
> @@ -678,6 +710,7 @@ static void __aer_print_error(struct pci_dev *dev,
> struct aer_err_info *info)
> {
> unsigned long status;
> + unsigned long anfe_status;
> const char **strings;
> const char *level, *errmsg;
> int i;
> @@ -700,6 +733,21 @@ static void __aer_print_error(struct pci_dev *dev,
> pci_printk(level, dev, " [%2d] %-22s%s\n", i, errmsg,
> info->first_error == i ? " (First)" : "");
> }
> +
> + if (info->severity == AER_CORRECTABLE && (status & PCI_ERR_COR_ADV_NFAT)) {
> + anfe_status = anfe_get_related_err(info);
> + if (anfe_status) {
> + pci_printk(level, dev, "Uncorrectable errors that may cause Advisory Non-Fatal:");
> + for_each_set_bit(i, &anfe_status, 32) {
> + errmsg = aer_uncorrectable_error_string[i];
> + if (!errmsg)
> + errmsg = "Unknown Error Bit";
> +
> + pci_printk(level, dev, " [%2d] %-22s\n", i, errmsg);
> + }
> + }
> + }
> +
> pci_dev_aer_stats_incr(dev, info);
> }
>
> @@ -1097,6 +1145,14 @@ static inline void cxl_rch_handle_error(struct pci_dev *dev,
> struct aer_err_info *info) { }
> #endif
>
> +static void handle_advisory_nonfatal(struct pci_dev *dev, struct aer_err_info *info)
> +{
> + int aer = dev->aer_cap;
> +
> + pci_write_config_dword(dev, aer + PCI_ERR_UNCOR_STATUS,
> + anfe_get_related_err(info));
> +}
> +
> /**
> * pci_aer_handle_error - handle logging error into an event log
> * @dev: pointer to pci_dev data structure of error source device
> @@ -1113,9 +1169,12 @@ 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->cor_status);
> + if (info->cor_status & PCI_ERR_COR_ADV_NFAT)
> + handle_advisory_nonfatal(dev, info);
> + }
> if (pcie_aer_is_native(dev)) {
> struct pci_driver *pdrv = dev->driver;
>
> --
> 2.42.0
>