Re: [PATCH v10 05/17] CXL/AER: Introduce kfifo for forwarding CXL errors

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

On 7/1/2025 4:53 PM, Dave Jiang wrote:
>
> On 6/26/25 3:42 PM, Terry Bowman wrote:
>> CXL error handling will soon be moved from the AER driver into the CXL
>> driver. This requires a notification mechanism for the AER driver to share
>> the AER interrupt with the CXL driver. The notification will be used
>> as an indication for the CXL drivers to handle and log the CXL RAS errors.
>>
>> First, introduce cxl/core/native_ras.c to contain changes for the CXL
>> driver's RAS native handling. This as an alternative to dropping the
>> changes into existing cxl/core/ras.c file with purpose to avoid #ifdefs.
>> Introduce CXL Kconfig CXL_NATIVE_RAS, dependent on PCIEAER_CXL, to
>> conditionally compile the new file.
>>
>> Add a kfifo work queue to be used by the AER driver and CXL driver. The AER
>> driver will be the sole kfifo producer adding work and the cxl_core will be
>> the sole kfifo consumer removing work. Add the boilerplate kfifo support.
>>
>> Add CXL work queue handler registration functions in the AER driver. Export
>> the functions allowing CXL driver to access. Implement registration
>> functions for the CXL driver to assign or clear the work handler function.
>>
>> Introduce 'struct cxl_proto_err_info' to serve as the kfifo work data. This
>> will contain the erring device's PCI SBDF details used to rediscover the
>> device after the CXL driver dequeues the kfifo work. The device rediscovery
>> will be introduced along with the CXL handling in future patches.
>>
>> Signed-off-by: Terry Bowman <terry.bowman@amd.com>
>> ---
>>  drivers/cxl/Kconfig           | 14 ++++++++
>>  drivers/cxl/core/Makefile     |  1 +
>>  drivers/cxl/core/core.h       |  8 +++++
>>  drivers/cxl/core/native_ras.c | 26 +++++++++++++++
> With the addition of a new file to cxl_core, can you please also fix up tools/testing/cxl/Kbuild?
>
> DJ
Hi Dave,

Yes, I'll update the CXL test's Kbuild.

-Terry

>>  drivers/cxl/core/port.c       |  2 ++
>>  drivers/cxl/core/ras.c        |  1 +
>>  drivers/cxl/cxlpci.h          |  1 +
>>  drivers/pci/pci.h             |  4 +++
>>  drivers/pci/pcie/aer.c        |  7 ++--
>>  drivers/pci/pcie/cxl_aer.c    | 60 +++++++++++++++++++++++++++++++++++
>>  include/linux/aer.h           | 31 ++++++++++++++++++
>>  11 files changed, 153 insertions(+), 2 deletions(-)
>>  create mode 100644 drivers/cxl/core/native_ras.c
>>
>> diff --git a/drivers/cxl/Kconfig b/drivers/cxl/Kconfig
>> index 48b7314afdb8..57274de54a45 100644
>> --- a/drivers/cxl/Kconfig
>> +++ b/drivers/cxl/Kconfig
>> @@ -233,4 +233,18 @@ config CXL_MCE
>>  	def_bool y
>>  	depends on X86_MCE && MEMORY_FAILURE
>>  
>> +config CXL_NATIVE_RAS
>> +	bool "CXL: Enable CXL RAS native handling"
>> +	depends on PCIEAER_CXL
>> +	default CXL_BUS
>> +	help
>> +	  Enable native CXL RAS protocol error handling and logging in the CXL
>> +	  drivers. This functionality relies on the AER service driver being
>> +	  enabled, as the AER interrupt is used to inform the operating system
>> +	  of CXL RAS protocol errors. The platform must be configured to
>> +	  utilize AER reporting for interrupts.
>> +
>> +	  If unsure, or if this kernel is meant for production environments,
>> +	  say Y.
>> +
>>  endif
>> diff --git a/drivers/cxl/core/Makefile b/drivers/cxl/core/Makefile
>> index 79e2ef81fde8..16f5832e5cc4 100644
>> --- a/drivers/cxl/core/Makefile
>> +++ b/drivers/cxl/core/Makefile
>> @@ -21,3 +21,4 @@ cxl_core-$(CONFIG_CXL_REGION) += region.o
>>  cxl_core-$(CONFIG_CXL_MCE) += mce.o
>>  cxl_core-$(CONFIG_CXL_FEATURES) += features.o
>>  cxl_core-$(CONFIG_CXL_EDAC_MEM_FEATURES) += edac.o
>> +cxl_core-$(CONFIG_CXL_NATIVE_RAS) += native_ras.o
>> diff --git a/drivers/cxl/core/core.h b/drivers/cxl/core/core.h
>> index 29b61828a847..4c08bb92e2f9 100644
>> --- a/drivers/cxl/core/core.h
>> +++ b/drivers/cxl/core/core.h
>> @@ -123,6 +123,14 @@ int cxl_gpf_port_setup(struct cxl_dport *dport);
>>  int cxl_acpi_get_extended_linear_cache_size(struct resource *backing_res,
>>  					    int nid, resource_size_t *size);
>>  
>> +#ifdef CONFIG_PCIEAER_CXL
>> +void cxl_native_ras_init(void);
>> +void cxl_native_ras_exit(void);
>> +#else
>> +static inline void cxl_native_ras_init(void) { };
>> +static inline void cxl_native_ras_exit(void) { };
>> +#endif
>> +
>>  #ifdef CONFIG_CXL_FEATURES
>>  struct cxl_feat_entry *
>>  cxl_feature_info(struct cxl_features_state *cxlfs, const uuid_t *uuid);
>> diff --git a/drivers/cxl/core/native_ras.c b/drivers/cxl/core/native_ras.c
>> new file mode 100644
>> index 000000000000..011815ddaae3
>> --- /dev/null
>> +++ b/drivers/cxl/core/native_ras.c
>> @@ -0,0 +1,26 @@
>> +// SPDX-License-Identifier: GPL-2.0-only
>> +/* Copyright(c) 2025 AMD Corporation. All rights reserved. */
>> +
>> +#include <linux/pci.h>
>> +#include <linux/aer.h>
>> +#include <cxl/event.h>
>> +#include <cxlmem.h>
>> +#include <core/core.h>
>> +
>> +static void cxl_proto_err_work_fn(struct work_struct *work)
>> +{
>> +}
>> +
>> +static struct work_struct cxl_proto_err_work;
>> +static DECLARE_WORK(cxl_proto_err_work, cxl_proto_err_work_fn);
>> +
>> +void cxl_native_ras_init(void)
>> +{
>> +	cxl_register_proto_err_work(&cxl_proto_err_work);
>> +}
>> +
>> +void cxl_native_ras_exit(void)
>> +{
>> +	cxl_unregister_proto_err_work();
>> +	cancel_work_sync(&cxl_proto_err_work);
>> +}
>> diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
>> index eb46c6764d20..8e8f21197c86 100644
>> --- a/drivers/cxl/core/port.c
>> +++ b/drivers/cxl/core/port.c
>> @@ -2345,6 +2345,8 @@ static __init int cxl_core_init(void)
>>  	if (rc)
>>  		goto err_ras;
>>  
>> +	cxl_native_ras_init();
>> +
>>  	return 0;
>>  
>>  err_ras:
>> diff --git a/drivers/cxl/core/ras.c b/drivers/cxl/core/ras.c
>> index 485a831695c7..962dc94fed8c 100644
>> --- a/drivers/cxl/core/ras.c
>> +++ b/drivers/cxl/core/ras.c
>> @@ -5,6 +5,7 @@
>>  #include <linux/aer.h>
>>  #include <cxl/event.h>
>>  #include <cxlmem.h>
>> +#include <cxlpci.h>
>>  #include "trace.h"
>>  
>>  static void cxl_cper_trace_corr_port_prot_err(struct pci_dev *pdev,
>> diff --git a/drivers/cxl/cxlpci.h b/drivers/cxl/cxlpci.h
>> index 54e219b0049e..6f1396ef7b77 100644
>> --- a/drivers/cxl/cxlpci.h
>> +++ b/drivers/cxl/cxlpci.h
>> @@ -4,6 +4,7 @@
>>  #define __CXL_PCI_H__
>>  #include <linux/pci.h>
>>  #include "cxl.h"
>> +#include "linux/aer.h"
>>  
>>  #define CXL_MEMORY_PROGIF	0x10
>>  
>> diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
>> index 91b583cf18eb..29c11c7136d3 100644
>> --- a/drivers/pci/pci.h
>> +++ b/drivers/pci/pci.h
>> @@ -1032,9 +1032,13 @@ static inline void pci_restore_aer_state(struct pci_dev *dev) { }
>>  #ifdef CONFIG_PCIEAER_CXL
>>  void cxl_rch_handle_error(struct pci_dev *dev, struct aer_err_info *info);
>>  void cxl_rch_enable_rcec(struct pci_dev *rcec);
>> +bool is_cxl_error(struct pci_dev *pdev, struct aer_err_info *info);
>> +void forward_cxl_error(struct pci_dev *pdev, struct aer_err_info *aer_err_info);
>>  #else
>>  static inline void cxl_rch_handle_error(struct pci_dev *dev, struct aer_err_info *info) { }
>>  static inline void cxl_rch_enable_rcec(struct pci_dev *rcec) { }
>> +static inline bool is_cxl_error(struct pci_dev *pdev, struct aer_err_info *info) { return false; }
>> +static inline void forward_cxl_error(struct pci_dev *pdev, struct aer_err_info *aer_err_info) { }
>>  #endif
>>  
>>  #ifdef CONFIG_ACPI
>> diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
>> index 0b4d721980ef..8417a49c71f2 100644
>> --- a/drivers/pci/pcie/aer.c
>> +++ b/drivers/pci/pcie/aer.c
>> @@ -1130,8 +1130,11 @@ 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_rch_handle_error(dev, info);
>> -	pci_aer_handle_error(dev, info);
>> +	if (is_cxl_error(dev, info))
>> +		forward_cxl_error(dev, info);
>> +	else
>> +		pci_aer_handle_error(dev, info);
>> +
>>  	pci_dev_put(dev);
>>  }
>>  
>> diff --git a/drivers/pci/pcie/cxl_aer.c b/drivers/pci/pcie/cxl_aer.c
>> index b2ea14f70055..846ab55d747c 100644
>> --- a/drivers/pci/pcie/cxl_aer.c
>> +++ b/drivers/pci/pcie/cxl_aer.c
>> @@ -3,8 +3,11 @@
>>  
>>  #include <linux/pci.h>
>>  #include <linux/aer.h>
>> +#include <linux/kfifo.h>
>>  #include "../pci.h"
>>  
>> +#define CXL_ERROR_SOURCES_MAX          128
>> +
>>  /**
>>   * pci_aer_unmask_internal_errors - unmask internal errors
>>   * @dev: pointer to the pci_dev data structure
>> @@ -64,6 +67,19 @@ static bool is_internal_error(struct aer_err_info *info)
>>  	return info->status & PCI_ERR_UNC_INTN;
>>  }
>>  
>> +bool is_cxl_error(struct pci_dev *pdev, struct aer_err_info *info)
>> +{
>> +	if (!info || !info->is_cxl)
>> +		return false;
>> +
>> +	/* Only CXL Endpoints are currently supported */
>> +	if ((pci_pcie_type(pdev) != PCI_EXP_TYPE_ENDPOINT) &&
>> +	    (pci_pcie_type(pdev) != PCI_EXP_TYPE_RC_EC))
>> +		return false;
>> +
>> +	return is_internal_error(info);
>> +}
>> +
>>  static int cxl_rch_handle_error_iter(struct pci_dev *dev, void *data)
>>  {
>>  	struct aer_err_info *info = (struct aer_err_info *)data;
>> @@ -136,3 +152,47 @@ void cxl_rch_enable_rcec(struct pci_dev *rcec)
>>  	pci_info(rcec, "CXL: Internal errors unmasked");
>>  }
>>  
>> +static DEFINE_KFIFO(cxl_proto_err_fifo, struct cxl_proto_err_work_data,
>> +		    CXL_ERROR_SOURCES_MAX);
>> +static DEFINE_SPINLOCK(cxl_proto_err_fifo_lock);
>> +struct work_struct *cxl_proto_err_work;
>> +
>> +void cxl_register_proto_err_work(struct work_struct *work)
>> +{
>> +	guard(spinlock)(&cxl_proto_err_fifo_lock);
>> +	cxl_proto_err_work = work;
>> +}
>> +EXPORT_SYMBOL_NS_GPL(cxl_register_proto_err_work, "CXL");
>> +
>> +void cxl_unregister_proto_err_work(void)
>> +{
>> +	guard(spinlock)(&cxl_proto_err_fifo_lock);
>> +	cxl_proto_err_work = NULL;
>> +}
>> +EXPORT_SYMBOL_NS_GPL(cxl_unregister_proto_err_work, "CXL");
>> +
>> +int cxl_proto_err_kfifo_get(struct cxl_proto_err_work_data *wd)
>> +{
>> +	return kfifo_get(&cxl_proto_err_fifo, wd);
>> +}
>> +EXPORT_SYMBOL_NS_GPL(cxl_proto_err_kfifo_get, "CXL");
>> +
>> +void forward_cxl_error(struct pci_dev *pdev, struct aer_err_info *aer_err_info)
>> +{
>> +	struct cxl_proto_err_work_data wd;
>> +
>> +	wd.err_info = (struct cxl_proto_error_info) {
>> +		.severity = aer_err_info->severity,
>> +		.devfn = pdev->devfn,
>> +		.bus = pdev->bus->number,
>> +		.segment = pci_domain_nr(pdev->bus)
>> +	};
>> +
>> +	if (!kfifo_put(&cxl_proto_err_fifo, wd)) {
>> +		dev_err_ratelimited(&pdev->dev, "CXL kfifo overflow\n");
>> +		return;
>> +	}
>> +
>> +	schedule_work(cxl_proto_err_work);
>> +}
>> +
>> diff --git a/include/linux/aer.h b/include/linux/aer.h
>> index 02940be66324..24c3d9e18ad5 100644
>> --- a/include/linux/aer.h
>> +++ b/include/linux/aer.h
>> @@ -10,6 +10,7 @@
>>  
>>  #include <linux/errno.h>
>>  #include <linux/types.h>
>> +#include <linux/workqueue_types.h>
>>  
>>  #define AER_NONFATAL			0
>>  #define AER_FATAL			1
>> @@ -53,6 +54,26 @@ struct aer_capability_regs {
>>  	u16 uncor_err_source;
>>  };
>>  
>> +/**
>> + * struct cxl_proto_err_info - Error information used in CXL error handling
>> + * @severity: AER severity
>> + * @function: Device's PCI function
>> + * @device: Device's PCI device
>> + * @bus: Device's PCI bus
>> + * @segment: Device's PCI segment
>> + */
>> +struct cxl_proto_error_info {
>> +	int severity;
>> +
>> +	u8 devfn;
>> +	u8 bus;
>> +	u16 segment;
>> +};
>> +
>> +struct cxl_proto_err_work_data {
>> +	struct cxl_proto_error_info err_info;
>> +};
>> +
>>  #if defined(CONFIG_PCIEAER)
>>  int pci_aer_clear_nonfatal_status(struct pci_dev *dev);
>>  int pcie_aer_is_native(struct pci_dev *dev);
>> @@ -64,6 +85,16 @@ static inline int pci_aer_clear_nonfatal_status(struct pci_dev *dev)
>>  static inline int pcie_aer_is_native(struct pci_dev *dev) { return 0; }
>>  #endif
>>  
>> +#if defined(CONFIG_PCIEAER_CXL)
>> +void cxl_register_proto_err_work(struct work_struct *work);
>> +void cxl_unregister_proto_err_work(void);
>> +int cxl_proto_err_kfifo_get(struct cxl_proto_err_work_data *wd);
>> +#else
>> +static inline void cxl_register_proto_err_work(struct work_struct *work) { }
>> +static inline void cxl_unregister_proto_err_work(void) { }
>> +static inline int cxl_proto_err_kfifo_get(struct cxl_proto_err_work_data *wd) { return 0; }
>> +#endif
>> +
>>  void pci_print_aer(struct pci_dev *dev, int aer_severity,
>>  		    struct aer_capability_regs *aer);
>>  int cper_severity_to_aer(int cper_severity);