Re: [PATCH v9 04/16] PCI/AER: Dequeue forwarded CXL error

From: Dave Jiang
Date: Fri Jun 06 2025 - 18:43:35 EST



On 6/6/25 11:14 AM, Bowman, Terry wrote:
>
>
> On 6/6/2025 10:57 AM, Dave Jiang wrote:
>>
>> On 6/3/25 10:22 AM, Terry Bowman wrote:
>>> The AER driver is now designed to forward CXL protocol errors to the CXL
>>> driver. Update the CXL driver with functionality to dequeue the forwarded
>>> CXL error from the kfifo. Also, update the CXL driver to begin the protocol
>>> error handling processing using the work received from the FIFO.
>>>
>>> Introduce function cxl_prot_err_work_fn() to dequeue work forwarded by the
>>> AER service driver. This will begin the CXL protocol error processing
>>> with a call to cxl_handle_prot_error().
>>>
>>> Update cxl/core/ras.c by adding cxl_rch_handle_error_iter() that was
>>> previously in the AER driver.
>>>
>>> Introduce sbdf_to_pci() to take the SBDF values from 'struct cxl_prot_error_info'
>>> and use in discovering the erring PCI device. Make scope based reference
>>> increments/decrements for the discovered PCI device and the associated
>>> CXL device.
>>>
>>> Implement cxl_handle_prot_error() to differentiate between Restricted CXL
>>> Host (RCH) protocol errors and CXL virtual host (VH) protocol errors.
>>> RCH errors will be processed with a call to walk the associated Root
>>> Complex Event Collector's (RCEC) secondary bus looking for the Root Complex
>>> Integrated Endpoint (RCiEP) to handle the RCH error. Export pcie_walk_rcec()
>>> so the CXL driver can walk the RCEC's downstream bus, searching for
>>> the RCiEP.
>>>
>>> VH correctable error (CE) processing will call the CXL CE handler. VH
>>> uncorrectable errors (UCE) will call cxl_do_recovery(), implemented as a
>>> stub for now and to be updated in future patch. Export pci_aer_clean_fatal_status()
>>> and pci_clean_device_status() used to clean up AER status after handling.
>>>
>>> Signed-off-by: Terry Bowman <terry.bowman@xxxxxxx>
>>> ---
>>> drivers/cxl/core/ras.c | 92 +++++++++++++++++++++++++++++++++++++++++
>>> drivers/pci/pci.c | 1 +
>>> drivers/pci/pci.h | 8 ----
>>> drivers/pci/pcie/aer.c | 1 +
>>> drivers/pci/pcie/rcec.c | 1 +
>>> include/linux/aer.h | 2 +
>>> include/linux/pci.h | 10 +++++
>>> 7 files changed, 107 insertions(+), 8 deletions(-)
>>>
>>> diff --git a/drivers/cxl/core/ras.c b/drivers/cxl/core/ras.c
>>> index d35525e79e04..9ed5c682e128 100644
>>> --- a/drivers/cxl/core/ras.c
>>> +++ b/drivers/cxl/core/ras.c
>>> @@ -110,8 +110,100 @@ static DECLARE_WORK(cxl_cper_prot_err_work, cxl_cper_prot_err_work_fn);
>>>
>>> #ifdef CONFIG_PCIEAER_CXL
>>>
>>> +static void cxl_do_recovery(struct pci_dev *pdev)
>>> +{
>>> +}
>>> +
>>> +static int cxl_rch_handle_error_iter(struct pci_dev *pdev, void *data)
>>> +{
>>> + struct cxl_prot_error_info *err_info = data;
>>> + struct pci_dev *pdev_ref __free(pci_dev_put) = pci_dev_get(pdev);
>>> + struct cxl_dev_state *cxlds;
>>> +
>>> + /*
>>> + * The capability, status, and control fields in Device 0,
>>> + * Function 0 DVSEC control the CXL functionality of the
>>> + * entire device (CXL 3.0, 8.1.3).
>>> + */
>>> + if (pdev->devfn != PCI_DEVFN(0, 0))
>>> + return 0;
>>> +
>>> + /*
>>> + * CXL Memory Devices must have the 502h class code set (CXL
>>> + * 3.0, 8.1.12.1).
>>> + */
>>> + if ((pdev->class >> 8) != PCI_CLASS_MEMORY_CXL)
>> Should use FIELD_GET() to be consistent with the rest of CXL code base
>
> Ok.
>
>>> + return 0;
>>> +
>>> + if (!is_cxl_memdev(&pdev->dev) || !pdev->dev.driver)
>> I think you need to hold the pdev->dev lock while checking if the driver exists.
> Ok.
>>> + return 0;
>>> +
>>> + cxlds = pci_get_drvdata(pdev);
>>> + struct device *dev __free(put_device) = get_device(&cxlds->cxlmd->dev);
>> Maybe a comment on why cxlmd->dev ref is needed here.
> Good point.
>>> +
>>> + if (err_info->severity == AER_CORRECTABLE)
>>> + cxl_cor_error_detected(pdev);
>>> + else
>>> + cxl_do_recovery(pdev);
>>> +
>>> + return 1;
>>> +}
>>> +
>>> +static struct pci_dev *sbdf_to_pci(struct cxl_prot_error_info *err_info)
>>> +{
>>> + unsigned int devfn = PCI_DEVFN(err_info->device,
>>> + err_info->function);
>>> + struct pci_dev *pdev __free(pci_dev_put) =
>>> + pci_get_domain_bus_and_slot(err_info->segment,
>>> + err_info->bus,
>>> + devfn);
>> Looks like DanC already caught that. Maybe have this function return with a ref held. I would also add a comment for the function mention that the caller need to put the device.
> Right. I made the change in v10 source after DanC commented. I'll add a comment that callers must decrement the reference count..
>>> + return pdev;
>>> +}
>>> +
>>> +static void cxl_handle_prot_error(struct cxl_prot_error_info *err_info)
>>> +{
>>> + struct pci_dev *pdev __free(pci_dev_put) = pci_dev_get(sbdf_to_pci(err_info));
>>> +
>>> + if (!pdev) {
>>> + pr_err("Failed to find the CXL device\n");
>>> + return;
>>> + }
>>> +
>>> + /*
>>> + * Internal errors of an RCEC indicate an AER error in an
>>> + * RCH's downstream port. Check and handle them in the CXL.mem
>>> + * device driver.
>>> + */
>>> + if (pci_pcie_type(pdev) == PCI_EXP_TYPE_RC_EC)
>>> + return pcie_walk_rcec(pdev, cxl_rch_handle_error_iter, err_info);
>>> +
>> cxl_rch_handle_error_iter() holds the pdev device lock when handling errors. Does the code block below need locking?
>>
>> DJ
> There is a guard_lock() in the EP CXL error handlers (cxl_error_detected()/cxl_cor_error_detected()). I have question about
> the same for the non-EP handlers added later: should we add the same guard() for the CXL port handlers? That is in following patch:
> [PATCH v9 13/16] cxl/pci: Introduce CXL Port protocol error handlers.

I would think so....

DJ

>
> Terry
>>> + if (err_info->severity == AER_CORRECTABLE) {
>>> + int aer = pdev->aer_cap;
>>> + struct cxl_dev_state *cxlds = pci_get_drvdata(pdev);
>>> + struct device *dev __free(put_device) = get_device(&cxlds->cxlmd->dev);
>>> +
>>> + if (aer)
>>> + pci_clear_and_set_config_dword(pdev,
>>> + aer + PCI_ERR_COR_STATUS,
>>> + 0, PCI_ERR_COR_INTERNAL);
>>> +
>>> + cxl_cor_error_detected(pdev);
>>> +
>>> + pcie_clear_device_status(pdev);
>>> + } else {
>>> + cxl_do_recovery(pdev);
>>> + }
>>> +}
>>> +
>>> static void cxl_prot_err_work_fn(struct work_struct *work)
>>> {
>>> + struct cxl_prot_err_work_data wd;
>>> +
>>> + while (cxl_prot_err_kfifo_get(&wd)) {
>>> + struct cxl_prot_error_info *err_info = &wd.err_info;
>>> +
>>> + cxl_handle_prot_error(err_info);
>>> + }
>>> }
>>>
>>> #else
>>> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
>>> index e77d5b53c0ce..524ac32b744a 100644
>>> --- a/drivers/pci/pci.c
>>> +++ b/drivers/pci/pci.c
>>> @@ -2328,6 +2328,7 @@ void pcie_clear_device_status(struct pci_dev *dev)
>>> pcie_capability_read_word(dev, PCI_EXP_DEVSTA, &sta);
>>> pcie_capability_write_word(dev, PCI_EXP_DEVSTA, sta);
>>> }
>>> +EXPORT_SYMBOL_NS_GPL(pcie_clear_device_status, "CXL");
>>> #endif
>>>
>>> /**
>>> diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
>>> index d6296500b004..3c54a5ed803e 100644
>>> --- a/drivers/pci/pci.h
>>> +++ b/drivers/pci/pci.h
>>> @@ -649,16 +649,10 @@ static inline bool pci_dpc_recovered(struct pci_dev *pdev) { return false; }
>>> void pci_rcec_init(struct pci_dev *dev);
>>> void pci_rcec_exit(struct pci_dev *dev);
>>> void pcie_link_rcec(struct pci_dev *rcec);
>>> -void pcie_walk_rcec(struct pci_dev *rcec,
>>> - int (*cb)(struct pci_dev *, void *),
>>> - void *userdata);
>>> #else
>>> static inline void pci_rcec_init(struct pci_dev *dev) { }
>>> static inline void pci_rcec_exit(struct pci_dev *dev) { }
>>> static inline void pcie_link_rcec(struct pci_dev *rcec) { }
>>> -static inline void pcie_walk_rcec(struct pci_dev *rcec,
>>> - int (*cb)(struct pci_dev *, void *),
>>> - void *userdata) { }
>>> #endif
>>>
>>> #ifdef CONFIG_PCI_ATS
>>> @@ -967,7 +961,6 @@ void pci_no_aer(void);
>>> void pci_aer_init(struct pci_dev *dev);
>>> void pci_aer_exit(struct pci_dev *dev);
>>> extern const struct attribute_group aer_stats_attr_group;
>>> -void pci_aer_clear_fatal_status(struct pci_dev *dev);
>>> int pci_aer_clear_status(struct pci_dev *dev);
>>> int pci_aer_raw_clear_status(struct pci_dev *dev);
>>> void pci_save_aer_state(struct pci_dev *dev);
>>> @@ -976,7 +969,6 @@ void pci_restore_aer_state(struct pci_dev *dev);
>>> static inline void pci_no_aer(void) { }
>>> static inline void pci_aer_init(struct pci_dev *d) { }
>>> static inline void pci_aer_exit(struct pci_dev *d) { }
>>> -static inline void pci_aer_clear_fatal_status(struct pci_dev *dev) { }
>>> static inline int pci_aer_clear_status(struct pci_dev *dev) { return -EINVAL; }
>>> static inline int pci_aer_raw_clear_status(struct pci_dev *dev) { return -EINVAL; }
>>> static inline void pci_save_aer_state(struct pci_dev *dev) { }
>>> diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
>>> index 5350fa5be784..6e88331c6303 100644
>>> --- a/drivers/pci/pcie/aer.c
>>> +++ b/drivers/pci/pcie/aer.c
>>> @@ -290,6 +290,7 @@ void pci_aer_clear_fatal_status(struct pci_dev *dev)
>>> if (status)
>>> pci_write_config_dword(dev, aer + PCI_ERR_UNCOR_STATUS, status);
>>> }
>>> +EXPORT_SYMBOL_GPL(pci_aer_clear_fatal_status);
>>>
>>> /**
>>> * pci_aer_raw_clear_status - Clear AER error registers.
>>> diff --git a/drivers/pci/pcie/rcec.c b/drivers/pci/pcie/rcec.c
>>> index d0bcd141ac9c..fb6cf6449a1d 100644
>>> --- a/drivers/pci/pcie/rcec.c
>>> +++ b/drivers/pci/pcie/rcec.c
>>> @@ -145,6 +145,7 @@ void pcie_walk_rcec(struct pci_dev *rcec, int (*cb)(struct pci_dev *, void *),
>>>
>>> walk_rcec(walk_rcec_helper, &rcec_data);
>>> }
>>> +EXPORT_SYMBOL_NS_GPL(pcie_walk_rcec, "CXL");
>>>
>>> void pci_rcec_init(struct pci_dev *dev)
>>> {
>>> diff --git a/include/linux/aer.h b/include/linux/aer.h
>>> index 550407240ab5..c9a18eca16f8 100644
>>> --- a/include/linux/aer.h
>>> +++ b/include/linux/aer.h
>>> @@ -77,12 +77,14 @@ struct cxl_prot_err_work_data {
>>>
>>> #if defined(CONFIG_PCIEAER)
>>> int pci_aer_clear_nonfatal_status(struct pci_dev *dev);
>>> +void pci_aer_clear_fatal_status(struct pci_dev *dev);
>>> int pcie_aer_is_native(struct pci_dev *dev);
>>> #else
>>> static inline int pci_aer_clear_nonfatal_status(struct pci_dev *dev)
>>> {
>>> return -EINVAL;
>>> }
>>> +static inline void pci_aer_clear_fatal_status(struct pci_dev *dev) { }
>>> static inline int pcie_aer_is_native(struct pci_dev *dev) { return 0; }
>>> #endif
>>>
>>> diff --git a/include/linux/pci.h b/include/linux/pci.h
>>> index bff3009f9ff0..cd53715d53f3 100644
>>> --- a/include/linux/pci.h
>>> +++ b/include/linux/pci.h
>>> @@ -1806,6 +1806,9 @@ extern bool pcie_ports_native;
>>>
>>> int pcie_set_target_speed(struct pci_dev *port, enum pci_bus_speed speed_req,
>>> bool use_lt);
>>> +void pcie_walk_rcec(struct pci_dev *rcec,
>>> + int (*cb)(struct pci_dev *, void *),
>>> + void *userdata);
>>> #else
>>> #define pcie_ports_disabled true
>>> #define pcie_ports_native false
>>> @@ -1816,8 +1819,15 @@ static inline int pcie_set_target_speed(struct pci_dev *port,
>>> {
>>> return -EOPNOTSUPP;
>>> }
>>> +
>>> +static inline void pcie_walk_rcec(struct pci_dev *rcec,
>>> + int (*cb)(struct pci_dev *, void *),
>>> + void *userdata) { }
>>> +
>>> #endif
>>>
>>> +void pcie_clear_device_status(struct pci_dev *dev);
>>> +
>>> #define PCIE_LINK_STATE_L0S (BIT(0) | BIT(1)) /* Upstr/dwnstr L0s */
>>> #define PCIE_LINK_STATE_L1 BIT(2) /* L1 state */
>>> #define PCIE_LINK_STATE_L1_1 BIT(3) /* ASPM L1.1 state */
>
>