Re: [PATCH v17 09/11] cxl: Update Endpoint AER uncorrectable handler

[Dave Jiang <dave.jiang@intel.com>]

On 5/5/26 10:30 AM, Terry Bowman wrote:
> The CXL cxl_core driver now implements protocol RAS support. PCI
> uncorrectable (UCE) protocol errors, however, continue to be reported via
> the AER capability and must still be handled by a PCI error recovery callback.
> UCE handling is required to provide direction for recovery.
> 
> Replace the existing cxl_error_detected() callback in cxl/pci.c with a new
> cxl_pci_error_detected() implementation that handles uncorrectable AER PCI
> protocol errors.
> 
> The handler decides solely based on the pci_channel_state_t parameter and
> does not access PCIe AER capability registers from .error_detected, matching
> the pattern used by other drivers including the NVMe and ixgbe drivers.
> CXL.cachemem-corrupting protocol errors are routed separately through the
> AER-CXL kfifo to cxl_handle_proto_error(), so cxl_pci does not need to
> second-guess the AER core's classification.
> 
> claude-opus-4.7 was used for research on PCI error state transitions and
> requirements.
> 
> Assisted-by: Claude:claude-opus-4.7
> Signed-off-by: Terry Bowman <terry.bowman@amd.com>
> 
> ---
> 
> Changes in v16->v17:
> - Rename pci_error_handlers struct instance to cxl_pci_error_handlers to
>   avoid shadowing the struct type tag.
> - Restore scoped_guard(device) and dev->driver check around AER read.
> - NULL-check find_cxl_port_by_dev() before deref of port->uport_dev.
> - Updated commit message. (Terry)
> - Add scope cleanup for port variable in cxl_pci_error_detected() (Terry)
> - Drop cxl_uncor_aer_present(), rely on AER state
> 
> Changes in v15->v16:
> - Update commit message (DaveJ)
> - s/cxl_handle_aer()/cxl_uncor_aer_present()/g (Jonathan)
> - cxl_uncor_aer_present(): Leave original result calculation based on
>   if a UCE is present and the provided state (Terry)
> - Add call to pci_print_aer(). AER fails to log because is upstream
>   link (Terry)
> 
> Changes in v14->v15:
> - Update commit message and title. Added Bjorn's ack.
> - Move CE and UCE handling logic here
> 
> Changes in v13->v14:
> - Add Dave Jiang's review-by
> - Update commit message & headline (Bjorn)
> - Refactor cxl_port_error_detected()/cxl_port_cor_error_detected() to
>   one line (Jonathan)
> - Remove cxl_walk_port() (Dan)
> - Remove cxl_pci_drv_bound(). Check for 'is_cxl' parent port is
>   sufficient (Dan)
> - Remove device_lock_if()
> - Combined CE and UCE here (Terry)
> 
> Changes in v12->v13:
> - Move get_pci_cxl_host_dev() and cxl_handle_proto_error() to Dequeue
>   patch (Terry)
> - Remove EP case in cxl_get_ras_base(), not used. (Terry)
> - Remove check for dport->dport_dev (Dave)
> - Remove whitespace (Terry)
> 
> Changes in v11->v12:
> - Add call to cxl_pci_drv_bound() in cxl_handle_proto_error() and
>   pci_to_cxl_dev()
> - Change cxl_error_detected() -> cxl_cor_error_detected()
> - Remove NULL variable assignments
> - Replace bus_find_device() with find_cxl_port_by_uport() for upstream
>   port searches.
> 
> Changes in v10->v11:
> - None
> ---
>  drivers/cxl/core/ras.c | 43 ++++++++++++++++--------------------------
>  drivers/cxl/cxlpci.h   |  8 ++++----
>  drivers/cxl/pci.c      |  6 +++---
>  3 files changed, 23 insertions(+), 34 deletions(-)
> 
> diff --git a/drivers/cxl/core/ras.c b/drivers/cxl/core/ras.c
> index 5cc4087c2807..a98ce0f412ad 100644
> --- a/drivers/cxl/core/ras.c
> +++ b/drivers/cxl/core/ras.c
> @@ -253,38 +253,27 @@ bool cxl_handle_ras(struct device *dev, u64 serial, void __iomem *ras_base)
>  	return true;
>  }
>  
> -pci_ers_result_t cxl_error_detected(struct pci_dev *pdev,
> -				    pci_channel_state_t state)
> +pci_ers_result_t cxl_pci_error_detected(struct pci_dev *pdev,
> +					pci_channel_state_t state)
>  {
> -	struct cxl_dev_state *cxlds = pci_get_drvdata(pdev);
> -	struct cxl_memdev *cxlmd = cxlds->cxlmd;
> -	struct device *dev = &cxlmd->dev;
> -	bool ue;
> +	struct cxl_dport *dport;
> +	struct cxl_port *port __free(put_cxl_port) =
> +		find_cxl_port_by_dev(&pdev->dev, &dport);

Move this to right before 'port' is being checked. It's ok to do inline var declaration with __free().

DJ

> +	struct cxl_memdev *cxlmd;
> +	struct device *dev;
>  
> -	scoped_guard(device, dev) {
> -		if (!dev->driver) {
> -			dev_warn(&pdev->dev,
> -				 "%s: memdev disabled, abort error handling\n",
> -				 dev_name(dev));
> -			return PCI_ERS_RESULT_DISCONNECT;
> -		}
> +	if (!port)
> +		return PCI_ERS_RESULT_DISCONNECT;
>  
> -		/*
> -		 * A frozen channel indicates an impending reset which is fatal to
> -		 * CXL.mem operation, and will likely crash the system. On the off
> -		 * chance the situation is recoverable dump the status of the RAS
> -		 * capability registers and bounce the active state of the memdev.
> -		 */
> -		ue = cxl_handle_ras(&cxlds->cxlmd->dev, pci_get_dsn(pdev),
> -				    cxlmd->endpoint->regs.ras);
> -	}
> +	cxlmd = to_cxl_memdev(port->uport_dev);
> +	dev = &cxlmd->dev;
>  
>  	switch (state) {
>  	case pci_channel_io_normal:
> -		if (ue) {
> -			device_release_driver(dev);
> -			return PCI_ERS_RESULT_NEED_RESET;
> -		}
> +		/*
> +		 * Non-fatal CXL protocol errors are handled asynchronously
> +		 * by the AER-CXL kfifo worker (cxl_proto_err_work_fn).
> +		 */
>  		return PCI_ERS_RESULT_CAN_RECOVER;
>  	case pci_channel_io_frozen:
>  		dev_warn(&pdev->dev,
> @@ -299,7 +288,7 @@ pci_ers_result_t cxl_error_detected(struct pci_dev *pdev,
>  	}
>  	return PCI_ERS_RESULT_NEED_RESET;
>  }
> -EXPORT_SYMBOL_NS_GPL(cxl_error_detected, "CXL");
> +EXPORT_SYMBOL_NS_GPL(cxl_pci_error_detected, "CXL");
>  
>  static void cxl_handle_proto_error(struct pci_dev *pdev, struct cxl_port *port,
>  				   struct cxl_dport *dport, int severity)
> diff --git a/drivers/cxl/cxlpci.h b/drivers/cxl/cxlpci.h
> index 06c46adcf0f6..8aeb80a4e573 100644
> --- a/drivers/cxl/cxlpci.h
> +++ b/drivers/cxl/cxlpci.h
> @@ -89,13 +89,13 @@ struct cxl_dev_state;
>  void read_cdat_data(struct cxl_port *port);
>  
>  #ifdef CONFIG_CXL_RAS
> -pci_ers_result_t cxl_error_detected(struct pci_dev *pdev,
> -				    pci_channel_state_t state);
> +pci_ers_result_t cxl_pci_error_detected(struct pci_dev *pdev,
> +					pci_channel_state_t state);
>  void devm_cxl_dport_rch_ras_setup(struct cxl_dport *dport);
>  void devm_cxl_port_ras_setup(struct cxl_port *port);
>  #else
> -static inline pci_ers_result_t cxl_error_detected(struct pci_dev *pdev,
> -						  pci_channel_state_t state)
> +static inline pci_ers_result_t cxl_pci_error_detected(struct pci_dev *pdev,
> +						      pci_channel_state_t state)
>  {
>  	return PCI_ERS_RESULT_NONE;
>  }
> diff --git a/drivers/cxl/pci.c b/drivers/cxl/pci.c
> index 5eb64ced0de5..6459f94f8fa8 100644
> --- a/drivers/cxl/pci.c
> +++ b/drivers/cxl/pci.c
> @@ -1000,8 +1000,8 @@ static void cxl_reset_done(struct pci_dev *pdev)
>  	}
>  }
>  
> -static const struct pci_error_handlers cxl_error_handlers = {
> -	.error_detected	= cxl_error_detected,
> +static const struct pci_error_handlers cxl_pci_error_handlers = {
> +	.error_detected	= cxl_pci_error_detected,
>  	.slot_reset	= cxl_slot_reset,
>  	.resume		= cxl_error_resume,
>  	.reset_done	= cxl_reset_done,
> @@ -1011,7 +1011,7 @@ static struct pci_driver cxl_pci_driver = {
>  	.name			= KBUILD_MODNAME,
>  	.id_table		= cxl_mem_pci_tbl,
>  	.probe			= cxl_pci_probe,
> -	.err_handler		= &cxl_error_handlers,
> +	.err_handler		= &cxl_pci_error_handlers,
>  	.dev_groups		= cxl_rcd_groups,
>  	.driver	= {
>  		.probe_type	= PROBE_PREFER_ASYNCHRONOUS,