Re: [RESEND v13 20/25] CXL/PCI: Introduce CXL Port protocol error handlers

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

On 11/4/25 10:03 AM, Terry Bowman wrote:
> Add CXL protocol error handlers for CXL Port devices (Root Ports,
> Downstream Ports, and Upstream Ports). Implement cxl_port_cor_error_detected()
> and cxl_port_error_detected() to handle correctable and uncorrectable errors
> respectively.
> 
> Introduce cxl_get_ras_base() to retrieve the cached RAS register base
> address for a given CXL port. This function supports CXL Root Ports,
> Downstream Ports, and Upstream Ports by returning their previously mapped
> RAS register addresses.
> 
> Add device lock assertions to protect against concurrent device or RAS
> register removal during error handling. The port error handlers require
> two device locks:
> 
> 1. The port's CXL parent device - RAS registers are mapped using devm_*
>    functions with the parent port as the host. Locking the parent prevents
>    the RAS registers from being unmapped during error handling.
> 
> 2. The PCI device (pdev->dev) - Locking prevents concurrent modifications
>    to the PCI device structure during error handling.
> 
> The lock assertions added here will be satisfied by device locks introduced
> in a subsequent patch.
> 
> Introduce get_pci_cxl_host_dev() to return the device responsible for
> managing the RAS register mapping. This function increments the reference
> count on the host device to prevent premature resource release during error
> handling. The caller is responsible for decrementing the reference count.
> For CXL endpoints, which manage resources without a separate host device,
> this function returns NULL.
> 
> Update the AER driver's is_cxl_error() to recognize CXL Port devices in
> addition to CXL Endpoints, as both now have CXL-specific error handlers.
> 
> Signed-off-by: Terry Bowman <terry.bowman@amd.com>
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
> 
> ---
> 
> 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/core.h       | 10 +++++++
>  drivers/cxl/core/port.c       |  7 ++---
>  drivers/cxl/core/ras.c        | 49 +++++++++++++++++++++++++++++++++++
>  drivers/pci/pcie/aer_cxl_vh.c |  5 +++-
>  4 files changed, 67 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/cxl/core/core.h b/drivers/cxl/core/core.h
> index b2c0ccd6803f..046ec65ed147 100644
> --- a/drivers/cxl/core/core.h
> +++ b/drivers/cxl/core/core.h
> @@ -157,6 +157,8 @@ void cxl_cor_error_detected(struct device *dev);
>  pci_ers_result_t pci_error_detected(struct pci_dev *pdev,
>  				    pci_channel_state_t error);
>  void pci_cor_error_detected(struct pci_dev *pdev);
> +pci_ers_result_t cxl_port_error_detected(struct device *dev);
> +void cxl_port_cor_error_detected(struct device *dev);
>  #else
>  static inline int cxl_ras_init(void)
>  {
> @@ -176,6 +178,11 @@ static inline pci_ers_result_t pci_error_detected(struct pci_dev *pdev,
>  	return PCI_ERS_RESULT_NONE;
>  }
>  static inline void pci_cor_error_detected(struct pci_dev *pdev) { }
> +static inline void cxl_port_cor_error_detected(struct device *dev) { }
> +static inline pci_ers_result_t cxl_port_error_detected(struct device *dev)
> +{
> +	return PCI_ERS_RESULT_NONE;
> +}
>  #endif /* CONFIG_CXL_RAS */
>  
>  /* Restricted CXL Host specific RAS functions */
> @@ -190,6 +197,9 @@ static inline void cxl_handle_rdport_errors(struct cxl_dev_state *cxlds) { }
>  #endif /* CONFIG_CXL_RCH_RAS */
>  
>  int cxl_gpf_port_setup(struct cxl_dport *dport);
> +struct cxl_port *find_cxl_port(struct device *dport_dev,
> +			       struct cxl_dport **dport);
> +struct cxl_port *find_cxl_port_by_uport(struct device *uport_dev);
>  
>  struct cxl_hdm;
>  int cxl_hdm_decode_init(struct cxl_dev_state *cxlds, struct cxl_hdm *cxlhdm,
> diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
> index b70e1b505b5c..d060f864cf2e 100644
> --- a/drivers/cxl/core/port.c
> +++ b/drivers/cxl/core/port.c
> @@ -1360,8 +1360,8 @@ static struct cxl_port *__find_cxl_port(struct cxl_find_port_ctx *ctx)
>  	return NULL;
>  }
>  
> -static struct cxl_port *find_cxl_port(struct device *dport_dev,
> -				      struct cxl_dport **dport)
> +struct cxl_port *find_cxl_port(struct device *dport_dev,
> +			       struct cxl_dport **dport)
>  {
>  	struct cxl_find_port_ctx ctx = {
>  		.dport_dev = dport_dev,
> @@ -1564,7 +1564,7 @@ static int match_port_by_uport(struct device *dev, const void *data)
>   * Function takes a device reference on the port device. Caller should do a
>   * put_device() when done.
>   */
> -static struct cxl_port *find_cxl_port_by_uport(struct device *uport_dev)
> +struct cxl_port *find_cxl_port_by_uport(struct device *uport_dev)
>  {
>  	struct device *dev;
>  
> @@ -1573,6 +1573,7 @@ static struct cxl_port *find_cxl_port_by_uport(struct device *uport_dev)
>  		return to_cxl_port(dev);
>  	return NULL;
>  }
> +EXPORT_SYMBOL_NS_GPL(find_cxl_port_by_uport, "CXL");
>  
>  static int update_decoder_targets(struct device *dev, void *data)
>  {
> diff --git a/drivers/cxl/core/ras.c b/drivers/cxl/core/ras.c
> index beb142054bda..142ca8794107 100644
> --- a/drivers/cxl/core/ras.c
> +++ b/drivers/cxl/core/ras.c
> @@ -145,6 +145,39 @@ static void cxl_dport_map_ras(struct cxl_dport *dport)
>  		dev_dbg(dev, "Failed to map RAS capability.\n");
>  }
>  
> +static void __iomem *cxl_get_ras_base(struct device *dev)
> +{
> +	struct pci_dev *pdev = to_pci_dev(dev);
> +
> +	switch (pci_pcie_type(pdev)) {
> +	case PCI_EXP_TYPE_ROOT_PORT:
> +	case PCI_EXP_TYPE_DOWNSTREAM:
> +	{
> +		struct cxl_dport *dport;
> +		struct cxl_port *port __free(put_cxl_port) = find_cxl_port(&pdev->dev, &dport);
> +
> +		if (!dport) {
> +			pci_err(pdev, "Failed to find the CXL device");
> +			return NULL;
> +		}
> +		return dport->regs.ras;

The RAS MMIO mapping is done via devm_cxl_iomap_block() and is a devres against the device. Without holding the device lock, the port driver can unbind and the address mapping may go away in the middle or before cxl_handle_cor_ras()/cxl_handle_ras() being called. I think you'll have to hold the port lock here and make sure that the port driver is bound before reading the RAS register? I think the dport ras should be covered under the port umbrella.

> +	}
> +	case PCI_EXP_TYPE_UPSTREAM:
> +	{
> +		struct cxl_port *port __free(put_cxl_port) = find_cxl_port_by_uport(&pdev->dev);
> +
> +		if (!port) {
> +			pci_err(pdev, "Failed to find the CXL device");
> +			return NULL;
> +		}
> +		return port->uport_regs.ras;

same here

DJ> +	}
> +	}
> +
> +	dev_warn_once(dev, "Error: Unsupported device type (%X)", pci_pcie_type(pdev));
> +	return NULL;
> +}
> +
>  /**
>   * cxl_dport_init_ras_reporting - Setup CXL RAS report on this dport
>   * @dport: the cxl_dport that needs to be initialized
> @@ -254,6 +287,22 @@ pci_ers_result_t cxl_handle_ras(struct device *dev, u64 serial, void __iomem *ra
>  	return PCI_ERS_RESULT_PANIC;
>  }
>  
> +void cxl_port_cor_error_detected(struct device *dev)
> +{
> +	void __iomem *ras_base = cxl_get_ras_base(dev);
> +
> +	cxl_handle_cor_ras(dev, 0, ras_base);
> +}
> +EXPORT_SYMBOL_NS_GPL(cxl_port_cor_error_detected, "CXL");
> +
> +pci_ers_result_t cxl_port_error_detected(struct device *dev)
> +{
> +	void __iomem *ras_base = cxl_get_ras_base(dev);
> +
> +	return cxl_handle_ras(dev, 0, ras_base);
> +}
> +EXPORT_SYMBOL_NS_GPL(cxl_port_error_detected, "CXL");
> +
>  void cxl_cor_error_detected(struct device *dev)
>  {
>  	struct cxl_memdev *cxlmd = to_cxl_memdev(dev);
> diff --git a/drivers/pci/pcie/aer_cxl_vh.c b/drivers/pci/pcie/aer_cxl_vh.c
> index 5dbc81341dc4..25f9512b57f7 100644
> --- a/drivers/pci/pcie/aer_cxl_vh.c
> +++ b/drivers/pci/pcie/aer_cxl_vh.c
> @@ -43,7 +43,10 @@ bool is_cxl_error(struct pci_dev *pdev, struct aer_err_info *info)
>  	if (!info || !info->is_cxl)
>  		return false;
>  
> -	if (pci_pcie_type(pdev) != PCI_EXP_TYPE_ENDPOINT)
> +	if ((pci_pcie_type(pdev) != PCI_EXP_TYPE_ENDPOINT) &&
> +	    (pci_pcie_type(pdev) != PCI_EXP_TYPE_ROOT_PORT) &&
> +	    (pci_pcie_type(pdev) != PCI_EXP_TYPE_UPSTREAM) &&
> +	    (pci_pcie_type(pdev) != PCI_EXP_TYPE_DOWNSTREAM))
>  		return false;
>  
>  	return is_internal_error(info);