Re: [PATCH v5 05/16] PCI/AER: Add CXL PCIe Port correctable error support in AER service driver

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

On 1/14/2025 5:20 AM, Jonathan Cameron wrote:
> On Tue, 14 Jan 2025 14:54:23 +0800
> Li Ming <ming.li@zohomail.com> wrote:
>
>> On 1/7/2025 10:38 PM, Terry Bowman wrote:
>>> The AER service driver supports handling Downstream Port Protocol Errors in
>>> Restricted CXL host (RCH) mode also known as CXL1.1. It needs the same
>>> functionality for CXL PCIe Ports operating in Virtual Hierarchy (VH)
>>> mode.[1]
>>>
>>> CXL and PCIe Protocol Error handling have different requirements that
>>> necessitate a separate handling path. The AER service driver may try to
>>> recover PCIe uncorrectable non-fatal errors (UCE). The same recovery is not
>>> suitable for CXL PCIe Port devices because of potential for system memory
>>> corruption. Instead, CXL Protocol Error handling must use a kernel panic
>>> in the case of a fatal or non-fatal UCE. The AER driver's PCIe Protocol
>>> Error handling does not panic the kernel in response to a UCE.
>>>
>>> Introduce a separate path for CXL Protocol Error handling in the AER
>>> service driver. This will allow CXL Protocol Errors to use CXL specific
>>> handling instead of PCIe handling. Add the CXL specific changes without
>>> affecting or adding functionality in the PCIe handling.
>>>
>>> Make this update alongside the existing Downstream Port RCH error handling
>>> logic, extending support to CXL PCIe Ports in VH mode.
>>>
>>> is_internal_error() is currently limited by CONFIG_PCIEAER_CXL kernel
>>> config. Update is_internal_error()'s function declaration such that it is
>>> always available regardless if CONFIG_PCIEAER_CXL kernel config is enabled
>>> or disabled.
>>>
>>> The uncorrectable error (UCE) handling will be added in a future patch.
>>>
>>> [1] CXL 3.1 Spec, 12.2.2 CXL Root Ports, Downstream Switch Ports, and
>>> Upstream Switch Ports
>>>
>>> Signed-off-by: Terry Bowman <terry.bowman@amd.com>
>>> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
>>> Reviewed-by: Dave Jiang <dave.jiang@intel.com>
>>> ---
>>>  drivers/pci/pcie/aer.c | 61 +++++++++++++++++++++++++++---------------
>>>  1 file changed, 40 insertions(+), 21 deletions(-)
>>>
>>> diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
>>> index f8b3350fcbb4..62be599e3bee 100644
>>> --- a/drivers/pci/pcie/aer.c
>>> +++ b/drivers/pci/pcie/aer.c
>>> @@ -942,8 +942,15 @@ static bool find_source_device(struct pci_dev *parent,
>>>  	return true;
>>>  }
>>>  
>>> -#ifdef CONFIG_PCIEAER_CXL
>>> +static bool is_internal_error(struct aer_err_info *info)
>>> +{
>>> +	if (info->severity == AER_CORRECTABLE)
>>> +		return info->status & PCI_ERR_COR_INTERNAL;
>>>  
>>> +	return info->status & PCI_ERR_UNC_INTN;
>>> +}
>>> +
>>> +#ifdef CONFIG_PCIEAER_CXL
>>>  /**
>>>   * pci_aer_unmask_internal_errors - unmask internal errors
>>>   * @dev: pointer to the pcie_dev data structure
>>> @@ -995,14 +1002,6 @@ static bool cxl_error_is_native(struct pci_dev *dev)
>>>  	return (pcie_ports_native || host->native_aer);
>>>  }
>>>  
>>> -static bool is_internal_error(struct aer_err_info *info)
>>> -{
>>> -	if (info->severity == AER_CORRECTABLE)
>>> -		return info->status & PCI_ERR_COR_INTERNAL;
>>> -
>>> -	return info->status & PCI_ERR_UNC_INTN;
>>> -}
>>> -
>>>  static int cxl_rch_handle_error_iter(struct pci_dev *dev, void *data)
>>>  {
>>>  	struct aer_err_info *info = (struct aer_err_info *)data;
>>> @@ -1034,14 +1033,23 @@ static int cxl_rch_handle_error_iter(struct pci_dev *dev, void *data)
>>>  
>>>  static void cxl_handle_error(struct pci_dev *dev, struct aer_err_info *info)
>>>  {
>>> -	/*
>>> -	 * 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(dev) == PCI_EXP_TYPE_RC_EC &&
>>> -	    is_internal_error(info))
>>> -		pcie_walk_rcec(dev, cxl_rch_handle_error_iter, info);
>>> +	if (pci_pcie_type(dev) == PCI_EXP_TYPE_RC_EC)
>>> +		return pcie_walk_rcec(dev, cxl_rch_handle_error_iter, info);
>>> +
>>> +	if (info->severity == AER_CORRECTABLE) {
>>> +		struct pci_driver *pdrv = dev->driver;
>>> +		int aer = dev->aer_cap;
>>> +
>>> +		if (aer)
>>> +			pci_write_config_dword(dev, aer + PCI_ERR_COR_STATUS,
>>> +					       info->status);
>>> +
>>> +		if (pdrv && pdrv->cxl_err_handler &&
>>> +		    pdrv->cxl_err_handler->cor_error_detected)
>>> +			pdrv->cxl_err_handler->cor_error_detected(dev);
>>> +
>>> +		pcie_clear_device_status(dev);
>>> +	}
>>>  }
>>>  
>>>  static int handles_cxl_error_iter(struct pci_dev *dev, void *data)
>>> @@ -1059,9 +1067,13 @@ static bool handles_cxl_errors(struct pci_dev *dev)
>>>  {
>>>  	bool handles_cxl = false;
>>>  
>>> -	if (pci_pcie_type(dev) == PCI_EXP_TYPE_RC_EC &&
>>> -	    pcie_aer_is_native(dev))
>>> +	if (!pcie_aer_is_native(dev))
>>> +		return false;
>>> +
>>> +	if (pci_pcie_type(dev) == PCI_EXP_TYPE_RC_EC)
>>>  		pcie_walk_rcec(dev, handles_cxl_error_iter, &handles_cxl);
>>> +	else
>>> +		handles_cxl = pcie_is_cxl_port(dev);  
>> My understanding is if a cxl RP/USP/DSP is working on PCIe mode, they are also possible to expose a DVSEC ID 3(CXL r3.1 section 9.12.3). In such case, the AER handler should be pci_aer_handle_error() rather than cxl_handle_error().
>>
>> pcie_is_cxl_port() only checks if there is a DVSEC ID 3, but I think it should also check if the cxl port is working on CXL mode, does it make more sense?
>>
>>
> Good spot.
>
> Agreed a check on the mode makes sense.
>
> Jonathan

Hi Jonathan,

I responded to you and Ming here:

https://lore.kernel.org/linux-cxl/20250107143852.3692571-1-terry.bowman@amd.com/T/#m74f758d744ae446db5d07c541dc84f0a1d57996e

Regards,
Terry
>> Ming
>>
>>>  
>>>  	return handles_cxl;
>>>  }
>>> @@ -1079,6 +1091,10 @@ static void cxl_enable_internal_errors(struct pci_dev *dev)
>>>  static inline void cxl_enable_internal_errors(struct pci_dev *dev) { }
>>>  static inline void cxl_handle_error(struct pci_dev *dev,
>>>  				    struct aer_err_info *info) { }
>>> +static bool handles_cxl_errors(struct pci_dev *dev)
>>> +{
>>> +	return false;
>>> +}
>>>  #endif
>>>  
>>>  /**
>>> @@ -1116,8 +1132,11 @@ static void pci_aer_handle_error(struct pci_dev *dev, struct aer_err_info *info)
>>>  
>>>  static void handle_error_source(struct pci_dev *dev, struct aer_err_info *info)
>>>  {
>>> -	cxl_handle_error(dev, info);
>>> -	pci_aer_handle_error(dev, info);
>>> +	if (is_internal_error(info) && handles_cxl_errors(dev))
>>> +		cxl_handle_error(dev, info);
>>> +	else
>>> +		pci_aer_handle_error(dev, info);
>>> +
>>>  	pci_dev_put(dev);
>>>  }
>>>    
>>
>>