Re: [RFC PATCH 3/9] PCI/portdrv: Update portdrv with an atomic notifier for reporting AER internal errors

Terry Bowman
2024-06-24T15:22:55Z

Hi Jonathan,

I added responses inline below.

On 6/20/24 07:30, Jonathan Cameron wrote:
> On Mon, 17 Jun 2024 15:04:05 -0500
> Terry Bowman <terry.bowman@amd.com> wrote:
>
>> PCIe port devices are bound to portdrv, the PCIe port bus driver. portdrv
>> does not implement an AER correctable handler (CE) but does implement the
>> AER uncorrectable error (UCE). The UCE handler is fairly straightforward
>> in that it only checks for frozen error state and returns the next step
>> for recovery accordingly.
>>
>> As a result, port devices relying on AER correctable internal errors (CIE)
>> and AER uncorrectable internal errors (UIE) will not be handled. Note,
>> the PCIe spec indicates AER CIE/UIE can be used to report implementation
>> specific errors.[1]
>>
>> CXL root ports, CXL downstream switch ports, and CXL upstream switch ports
>> are examples of devices using the AER CIE/UIE for implementation specific
>> purposes. These CXL ports use the AER interrupt and AER CIE/UIE status to
>> report CXL RAS errors.[2]
>>
>> Add an atomic notifier to portdrv's CE/UCE handlers. Use the atomic
>> notifier to report CIE/UIE errors to the registered functions. This will
>> require adding a CE handler and updating the existing UCE handler.
>>
>> For the UCE handler, the CXL spec states UIE errors should return need
>> reset: "The only method of recovering from an Uncorrectable Internal Error
>> is reset or hardware replacement."[1]
>>
>> [1] PCI6.0 - 6.2.10 Internal Errors
>> [2] CXL3.1 - 12.2.2 CXL Root Ports, Downstream Switch Ports, and
>> Upstream Switch Ports
>>
>> Signed-off-by: Terry Bowman <terry.bowman@amd.com>
>> Cc: Bjorn Helgaas <bhelgaas@google.com>
>> Cc: linux-pci@vger.kernel.org
>> ---
>> drivers/pci/pcie/portdrv.c | 32 ++++++++++++++++++++++++++++++++
>> drivers/pci/pcie/portdrv.h | 2 ++
>> 2 files changed, 34 insertions(+)
>>
>> diff --git a/drivers/pci/pcie/portdrv.c b/drivers/pci/pcie/portdrv.c
>> index 14a4b89a3b83..86d80e0e9606 100644
>> --- a/drivers/pci/pcie/portdrv.c
>> +++ b/drivers/pci/pcie/portdrv.c
>> @@ -37,6 +37,9 @@ struct portdrv_service_data {
>> u32 service;
>> };
>>
>> +ATOMIC_NOTIFIER_HEAD(portdrv_aer_internal_err_chain);
>> +EXPORT_SYMBOL_GPL(portdrv_aer_internal_err_chain);
>
> Perhaps these should be per instance of the portdrv?
> I'd imagine we only want to register CXL ones on CXL ports etc
> and it's annoying to have to check at runtime for relevance
> of a particular notifier.
>

This could be made per-instance by moving to the PCI/device drvdata. This
would likely need a portdrv setup-init helper function to enable for a
particular PCI device.

>> +
>> /**
>> * release_pcie_device - free PCI Express port service device structure
>> * @dev: Port service device to release
>> @@ -745,11 +748,39 @@ static void pcie_portdrv_shutdown(struct pci_dev *dev)
>> static pci_ers_result_t pcie_portdrv_error_detected(struct pci_dev *dev,
>> pci_channel_state_t error)
>> {
>> + if (dev->aer_cap) {
>> + u32 status;
>> +
>> + pci_read_config_dword(dev, dev->aer_cap + PCI_ERR_UNCOR_STATUS,
>> + &status);
>> +
>> + if (status & PCI_ERR_UNC_INTN) {
>> + atomic_notifier_call_chain(&portdrv_aer_internal_err_chain,
>> + AER_FATAL, (void *)dev);
>
> Don't think the cast is needed as always fine to implicitly cast to and from
> void * in C.
>

Ok.

>> + return PCI_ERS_RESULT_NEED_RESET;
>> + }
>> + }
>> +
>> if (error == pci_channel_io_frozen)
>> return PCI_ERS_RESULT_NEED_RESET;
>> return PCI_ERS_RESULT_CAN_RECOVER;
>> }
>>
>> +static void pcie_portdrv_cor_error_detected(struct pci_dev *dev)
>> +{
>> + u32 status;
>> +
>> + if (!dev->aer_cap)
>> + return;
>> +
>> + pci_read_config_dword(dev, dev->aer_cap + PCI_ERR_COR_STATUS,
>> + &status);
>> +
>> + if (status & PCI_ERR_COR_INTERNAL)
>> + atomic_notifier_call_chain(&portdrv_aer_internal_err_chain,
>> + AER_CORRECTABLE, (void *)dev);
>
> No need for the cast.
>

Ok

Regards,
Terry

>> +}
>> +
>> static pci_ers_result_t pcie_portdrv_slot_reset(struct pci_dev *dev)
>> {
>> size_t off = offsetof(struct pcie_port_service_driver, slot_reset);
>> @@ -780,6 +811,7 @@ static const struct pci_device_id port_pci_ids[] = {
>>
>> static const struct pci_error_handlers pcie_portdrv_err_handler = {
>> .error_detected = pcie_portdrv_error_detected,
>> + .cor_error_detected = pcie_portdrv_cor_error_detected,
>> .slot_reset = pcie_portdrv_slot_reset,
>> .mmio_enabled = pcie_portdrv_mmio_enabled,
>> };
>> diff --git a/drivers/pci/pcie/portdrv.h b/drivers/pci/pcie/portdrv.h
>> index 12c89ea0313b..8a39197f0203 100644
>> --- a/drivers/pci/pcie/portdrv.h
>> +++ b/drivers/pci/pcie/portdrv.h
>> @@ -121,4 +121,6 @@ static inline void pcie_pme_interrupt_enable(struct pci_dev *dev, bool en) {}
>> #endif /* !CONFIG_PCIE_PME */
>>
>> struct device *pcie_port_find_device(struct pci_dev *dev, u32 service);
>> +
>> +extern struct atomic_notifier_head portdrv_aer_internal_err_chain;
>> #endif /* _PORTDRV_H_ */
>