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Message-ID: <SJ0PR11MB6744EC971D1BE6F3119EEA9992112@SJ0PR11MB6744.namprd11.prod.outlook.com>
Date: Tue, 23 Apr 2024 02:25:05 +0000
From: "Duan, Zhenzhong" <zhenzhong.duan@...el.com>
To: Jonathan Cameron <Jonathan.Cameron@...wei.com>
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<qingshun.wang@...ux.intel.com>
Subject: RE: [PATCH v3 1/3] PCI/AER: Store UNCOR_STATUS bits that might be
ANFE in aer_err_info
>-----Original Message-----
>From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
>Subject: Re: [PATCH v3 1/3] PCI/AER: Store UNCOR_STATUS bits that might
>be ANFE in aer_err_info
>
>On Wed, 17 Apr 2024 14:14:05 +0800
>Zhenzhong Duan <zhenzhong.duan@...el.com> wrote:
>
>> In some cases the detector of a Non-Fatal Error(NFE) is not the most
>> appropriate agent to determine the type of the error. For example,
>> when software performs a configuration read from a non-existent
>> device or Function, completer will send an ERR_NONFATAL Message.
>> On some platforms, ERR_NONFATAL results in a System Error, which
>> breaks normal software probing.
>>
>> Advisory Non-Fatal Error(ANFE) is a special case that can be used
>> in above scenario. It is predominantly determined by the role of the
>> detecting agent (Requester, Completer, or Receiver) and the specific
>> error. In such cases, an agent with AER signals the NFE (if enabled)
>> by sending an ERR_COR Message as an advisory to software, instead of
>> sending ERR_NONFATAL.
>>
>> 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, a Fatal
>> Error(FE) or Non-Fatal Error(NFE) may set the same UE status bit as
>> ANFE. Treating an ANFE as NFE will reproduce above mentioned issue,
>> i.e., breaking softwore probing; treating NFE as ANFE will make us
>> ignoring some UEs which need active recover operation. To avoid clearing
>> UEs that are not ANFE by accident, the most conservative route is taken
>> here: If any of the FE/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.
>>
>> To achieve above purpose, store UNCOR_STATUS bits that might be ANFE
>> in aer_err_info.anfe_status. So that those bits could be printed and
>> processed later.
>>
>> Tested-by: Yudong Wang <yudong.wang@...el.com>
>> Co-developed-by: "Wang, Qingshun" <qingshun.wang@...ux.intel.com>
>> Signed-off-by: "Wang, Qingshun" <qingshun.wang@...ux.intel.com>
>> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@...el.com>
>> ---
>> drivers/pci/pci.h | 1 +
>> drivers/pci/pcie/aer.c | 45
>++++++++++++++++++++++++++++++++++++++++++
>> 2 files changed, 46 insertions(+)
>>
>> diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
>> index 17fed1846847..3f9eb807f9fd 100644
>> --- a/drivers/pci/pci.h
>> +++ b/drivers/pci/pci.h
>> @@ -412,6 +412,7 @@ struct aer_err_info {
>>
>> unsigned int status; /* COR/UNCOR Error Status */
>> unsigned int mask; /* COR/UNCOR Error Mask */
>> + unsigned int anfe_status; /* UNCOR Error Status for ANFE */
>> struct pcie_tlp_log tlp; /* TLP Header */
>> };
>>
>> diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
>> index ac6293c24976..27364ab4b148 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);
>>
>> @@ -1196,6 +1202,41 @@ void aer_recover_queue(int domain, unsigned
>int bus, unsigned int devfn,
>> EXPORT_SYMBOL_GPL(aer_recover_queue);
>> #endif
>>
>> +static void anfe_get_uc_status(struct pci_dev *dev, struct aer_err_info
>*info)
>> +{
>> + u32 uncor_mask, uncor_status;
>> + u16 device_status;
>> + int aer = dev->aer_cap;
>> +
>> + if (pcie_capability_read_word(dev, PCI_EXP_DEVSTA,
>&device_status))
>> + return;
>> + /*
>> + * 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 (device_status & (PCI_EXP_DEVSTA_NFED | PCI_EXP_DEVSTA_FED))
>> + return;
>> +
>
>Is there not a race here? If we happen to get either an NFED or FED
>between the read of device_status above and here we might pick up a status
>that corresponds to that (and hence clear something we should not).
In this scenario, info->anfe_status is 0.
>
>Or am I missing that race being close somewhere?
The bits leading to NFED or FED is masked out when assigning info->anfe_status.
Bits for FED is masked out by ~info->severity,
bit for NFED is masked out by AER_ERR_ANFE_UNC_MASK.
So we never clear status bits for NFED or FED in ANFE handler.
See below assignment of info->anfe_status.
Thanks
Zhenzhong
>
>> + pci_read_config_dword(dev, aer + PCI_ERR_UNCOR_STATUS,
>&uncor_status);
>> + pci_read_config_dword(dev, aer + PCI_ERR_UNCOR_MASK,
>&uncor_mask);
>> + /*
>> + * According to PCIe Base Specification Revision 6.1,
>> + * Section 6.2.3.2.4, if an UNCOR error is raised 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 (Section 6.2.3.2.4.3)
>> + * 2. Completion Timeout (Section 6.2.3.2.4.4)
>> + * 3. Completer Abort (Section 6.2.3.2.4.1)
>> + * 4. Unexpected Completion (Section 6.2.3.2.4.5)
>> + * 5. Unsupported Request (Section 6.2.3.2.4.1)
>> + */
>> + info->anfe_status = uncor_status & ~uncor_mask & ~info->severity
>&
>> + AER_ERR_ANFE_UNC_MASK;
>> +}
>> +
>> /**
>> * aer_get_device_error_info - read error status from dev and store it to
>info
>> * @dev: pointer to the device expected to have a error record
>> @@ -1213,6 +1254,7 @@ int aer_get_device_error_info(struct pci_dev
>*dev, struct aer_err_info *info)
>>
>> /* Must reset in this function */
>> info->status = 0;
>> + info->anfe_status = 0;
>> info->tlp_header_valid = 0;
>>
>> /* The device might not support AER */
>> @@ -1226,6 +1268,9 @@ int aer_get_device_error_info(struct pci_dev
>*dev, struct aer_err_info *info)
>> &info->mask);
>> if (!(info->status & ~info->mask))
>> return 0;
>> +
>> + if (info->status & PCI_ERR_COR_ADV_NFAT)
>> + anfe_get_uc_status(dev, info);
>> } else if (type == PCI_EXP_TYPE_ROOT_PORT ||
>> type == PCI_EXP_TYPE_RC_EC ||
>> type == PCI_EXP_TYPE_DOWNSTREAM ||
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