Re: [PATCH v18 10/13] cxl: Add port and dport identifiers to CXL AER trace events

["Bowman, Terry" <terry.bowman@amd.com>]

On 7/20/2026 7:00 PM, Jonathan Cameron wrote:
> On Fri, 17 Jul 2026 17:27:03 -0500
> Terry Bowman <terry.bowman@amd.com> wrote:
> 
>> From: Dan Williams <djbw@kernel.org>
>>
>> Pass struct cxl_port * and struct cxl_dport * to the cxl_aer_*
>> trace events instead of a plain struct device * derived at the
>> caller. The trace event helpers then derive the right strings for
>> endpoints, switch ports, root ports, and RCH downstream ports
>> consistently across the CPER and native AER paths.
>>
>> The unified cxl_aer_* events keep "memdev" as the legacy field
>> (endpoint events populate it with the memdev name; non-endpoint
>> events emit memdev="") and add new "port" and "dport" string fields
>> populated for all CXL device classes. Updated userspace can key
>> off "port" and "dport" without a parallel set of events.
>>
>> Remove the separate cxl_port_aer_uncorrectable_error and
>> cxl_port_aer_correctable_error trace events. All CXL AER events now
>> use the unified cxl_aer_* events with port and dport fields.
>>
>> Rework cxl_cper_handle_prot_err() to use find_cxl_port_by_dev() and
>> the unified trace helpers, replacing the per-port-type branching and
>> bus_find_device() memdev lookup.
>>
>> The TP_printk format string places "port=%s dport=%s" between
>> "memdev=%s" and "host=%s", changing the text-mode field order from
>> the pre-patch output. This does not affect consumers such as
>> rasdaemon that use libtraceevent to parse fields by name rather than
>> by fixed text position.
>>
>> For non-endpoint events (switch port, root port, RCH dport),
>> "memdev" is empty and "port"/"dport" carry the topology information.
>>
>> The serial number is retrieved via pci_get_dsn() which performs live
>> PCI configuration space reads. A following patch ("PCI: Cache PCI
>> DSN into pci_dev->dsn during probe") replaces these with a cached
>> serial number to avoid config space access in error handlers and panic
>> paths.
>>
>> Below are examples of the different CXL devices' error trace logs
>> after this patch:
>>
>>      ---------------------
>>      | CXL RP - 0C:00.0  |
>>      ---------------------
>>                |
>>      ---------------------
>>      | CXL USP - 0D:00.0 |
>>      ---------------------
>>                |
>>      --------------------
>>      | CXL DSP - 0E:00.0 |
>>      --------------------
>>                |
>>      ---------------------
>>      | CXL EP - 0F:00.0  |
>>      ---------------------
>>
>> Root Port:
>> cxl_aer_correctable_error: memdev= port=port1 dport=0000:0c:00.0 \
>>    host=pci0000:0c serial=0: status: 'Memory Data ECC Error'
>>
>> cxl_aer_uncorrectable_error: memdev= port=port1 dport=0000:0c:00.0 \
>>    host=pci0000:0c serial=0: status: 'Cache Address Parity Error'  \
>>    first_error: 'Cache Address Parity Error'
>>
>> Upstream Switch Port:
>> cxl_aer_correctable_error: memdev= port=port2 dport= host=0000:0d:00.0 \
>>    serial=0: status: 'Memory Data ECC Error'
>>
>> UCE NA - Upstream Switch Port UCE's are handled in the portdrv driver's
>> PCI AER callbacks that are not CXL aware.
>>
>> Downstream Switch Port:
>> cxl_aer_correctable_error: memdev= port=port2 dport=0000:0e:00.0 \
>>    host=0000:0d:00.0 serial=0: status: 'Memory Data ECC Error'
>>
>> cxl_aer_uncorrectable_error: memdev= port=port2 dport=0000:0e:00.0 \
>>    host=0000:0d:00.0 serial=0: status: 'Cache Address Parity Error' \
>>    first_error: 'Cache Address Parity Error'
>>
>> Endpoint:
>> cxl_aer_uncorrectable_error: memdev=mem1 port=endpoint4 dport= \
>>    host=0000:0f:00.0 serial=0: status: 'Cache Address Parity Error' \
>>    first_error: 'Cache Address Parity Error'
>>
>> cxl_aer_correctable_error: memdev=mem1 port=endpoint4 dport= host=0000:0f:00.0 \
>>    serial=0: status: 'Memory Data ECC Error'
>>
>> Co-developed-by: Terry Bowman <terry.bowman@amd.com>
>> Signed-off-by: Terry Bowman <terry.bowman@amd.com>
>> Signed-off-by: Dan Williams <djbw@kernel.org>
> 
> One question inline about reference counts for the port.
> 
>>
>> diff --git a/drivers/cxl/core/ras.c b/drivers/cxl/core/ras.c
>> index d5dc2c22565da..acf40b2396c3b 100644
>> --- a/drivers/cxl/core/ras.c
>> +++ b/drivers/cxl/core/ras.c
> ...
>>  
>> @@ -109,47 +77,34 @@ static struct cxl_port *find_cxl_port_by_dev(struct device *dev, struct cxl_dpor
>>  
>>  void cxl_cper_handle_prot_err(struct cxl_cper_prot_err_work_data *data)
>>  {
>> +	struct cxl_dport *dport;
>>  	unsigned int devfn = PCI_DEVFN(data->prot_err.agent_addr.device,
>>  				       data->prot_err.agent_addr.function);
>> -	struct pci_dev *pdev __free(pci_dev_put) =
>> -		pci_get_domain_bus_and_slot(data->prot_err.agent_addr.segment,
>> -					    data->prot_err.agent_addr.bus,
>> -					    devfn);
>> -	struct cxl_memdev *cxlmd;
>> -	int port_type;
>> -
>> -	if (!pdev)
>> -		return;
>> -
>> -	port_type = pci_pcie_type(pdev);
>> -	if (port_type == PCI_EXP_TYPE_ROOT_PORT ||
>> -	    port_type == PCI_EXP_TYPE_DOWNSTREAM ||
>> -	    port_type == PCI_EXP_TYPE_UPSTREAM) {
>> -		if (data->severity == AER_CORRECTABLE)
>> -			cxl_cper_trace_corr_port_prot_err(pdev, data->ras_cap);
>> -		else
>> -			cxl_cper_trace_uncorr_port_prot_err(pdev, data->ras_cap);
>> -
>> +	struct pci_dev *pdev __free(pci_dev_put) = pci_get_domain_bus_and_slot(
>> +		data->prot_err.agent_addr.segment, data->prot_err.agent_addr.bus, devfn);
>> +	if (!pdev) {
>> +		pr_err_ratelimited("Failed to find CPER device in CXL topology\n");
>>  		return;
>>  	}
>>  
>> -	guard(device)(&pdev->dev);
>> -	if (!pdev->dev.driver) {
>> -		dev_warn_ratelimited(&pdev->dev,
>> -				     "Device is unbound, abort CPER error handling\n");
>> +	struct cxl_port *port __free(put_cxl_port) = find_cxl_port_by_dev(&pdev->dev, NULL);
>> +	if (!port) {
>> +		dev_err_ratelimited(&pdev->dev,
>> +				    "Failed to find parent port device in CXL topology\n");
>>  		return;
>>  	}
>>  
>> -	struct device *mem_dev __free(put_device) = bus_find_device(
>> -		&cxl_bus_type, NULL, pdev, match_memdev_by_parent);
>> -	if (!mem_dev)
>> -		return;
>> +	guard(device)(&port->dev);
> 
> Don't we have a reference for this from find_cxl_port_by_dev()?
> 
> Superficially scope looks the same.
> 
> 

I somehow missed this yesterday. Yes, find_cxl_port_by_dev() ref increments. 

>> +
>> +	/* dport is NULL for Endpoint and Upstream Port devices */
>> +	dport = cxl_find_dport_by_dev(port, &pdev->dev);
>>  
>> -	cxlmd = to_cxl_memdev(mem_dev);
>>  	if (data->severity == AER_CORRECTABLE)
>> -		cxl_cper_trace_corr_prot_err(cxlmd, data->ras_cap);
>> +		cxl_cper_trace_corr_prot_err(port, dport, pci_get_dsn(pdev),
>> +					     &data->ras_cap);
>>  	else
>> -		cxl_cper_trace_uncorr_prot_err(cxlmd, data->ras_cap);
>> +		cxl_cper_trace_uncorr_prot_err(port, dport, pci_get_dsn(pdev),
>> +					       &data->ras_cap);
>>  }
>>  EXPORT_SYMBOL_GPL(cxl_cper_handle_prot_err);
>>  
>> @@ -240,14 +195,14 @@ void cxl_do_recovery(struct pci_dev *pdev, struct cxl_port *port, struct cxl_dpo
>>  		return;
>>  	}
>>  
>> -	if (cxl_handle_ras(port, dport, ras_base))
>> +	if (cxl_handle_ras(port, dport, ras_base, pci_get_dsn(pdev)))
>>  		panic("CXL cachemem error");
>>  
>>  	dev_dbg(&pdev->dev,
>>  		"CXL UCE signaled but no CXL RAS status bits set\n");
>>  }
>>  
>> -void cxl_handle_cor_ras(struct cxl_port *port, struct cxl_dport *dport, void __iomem *ras_base)
>> +void cxl_handle_cor_ras(struct cxl_port *port, struct cxl_dport *dport, void __iomem *ras_base, u64 serial)
> That's over even the modern 100 char limit. Needs a line break.
>>  {
> 

Yup, I'll linewrap at 75-80. Thanks.

- Terry