Re: [RFC] cxl: Device protocol AER injection

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

On 7/20/2026 12:38 PM, Dave Jiang wrote:
> 
> 
> On 7/17/26 3:57 PM, Terry Bowman wrote:
>> This patch is intended to provide a method of testing the recently submitted
>> cxl series "cxl: Enable CXL PCIe Port Protocol Error handling and logging" found
>> here:
>>
>> https://lore.kernel.org/linux-cxl/20260717222706.3540281-1-terry.bowman@amd.com/T/#md90ec1fdd1b374bf1e32e7736e2b3e34b328c701
>>
>> The changes in this patch will allow CXL RAS protocol testing by injecting
>> AER errors using AER EINJ. The RAS register block status is updated
>> using a central function to augment RAS register block returned by
>> to_ras_base(). This supports all CXL devices including Root Ports,
>> Upstream Switch Ports, Downstream Switch Ports, Endpoints, and RCH
>> Downstream Ports.
>>
>> Add debugfs-based CXL protocol error injection for testing CXL RAS
>> error handling paths. Injects CXL RAS protocol errors using AER internal
>> error inject interface via /sys/kernel/debug/cxl/aer_einj_inject.
>>
>> RAS CXL status is set using to_ras_base() function override when kernel config
>> CONFIG_CXL_PROTO_AER_EINJ is enabled.
>>
>> Usage:
>>   echo "DDDD:BB:DD.F [UCE|CE] AER_STATUS RAS_STATUS [RCH]" > \
>>       /sys/kernel/debug/cxl/aer_einj_inject
>>
>> Move struct aer_error_inj and aer_inject() to linux/aer.h so CXL
>> can invoke AER injection directly. Export aer_inject() with
>> EXPORT_SYMBOL_GPL.
>>
>> Make cxl_debugfs non-static in port.c and declare it extern in
>> core.h so the debugfs file can be created under the existing CXL
>> debugfs root.
>>
>> Co-developed-by: Ben Cheatham <Benjamin.Cheatham@amd.com>
>> Signed-off-by: Ben Cheatham <Benjamin.Cheatham@amd.com>
>> Signed-off-by: Terry Bowman <terry.bowman@amd.com>
>> ---
>>  drivers/cxl/Kconfig           |  13 +++
>>  drivers/cxl/core/core.h       |  21 ++++
>>  drivers/cxl/core/port.c       |   2 +-
>>  drivers/cxl/core/ras.c        | 208 ++++++++++++++++++++++++++++++++++
>>  drivers/cxl/core/ras_rch.c    |  12 ++
>>  drivers/pci/pcie/aer_inject.c |  29 ++---
>>  include/linux/aer.h           |  15 +++
>>  7 files changed, 281 insertions(+), 19 deletions(-)
>>
>> diff --git a/drivers/cxl/Kconfig b/drivers/cxl/Kconfig
>> index 80aeb0d556bd7..ef449228b2549 100644
>> --- a/drivers/cxl/Kconfig
>> +++ b/drivers/cxl/Kconfig
>> @@ -238,6 +238,19 @@ config CXL_RAS
>>  	def_bool y
>>  	depends on ACPI_APEI_GHES && PCIEAER && CXL_BUS
>>  
>> +config CXL_PROTO_AER_EINJ
>> +	bool "CXL: RAS Protocol Error Injection using AER EINJ"
>> +	depends on CXL_RAS
>> +	depends on PCIEAER_INJECT
>> +	help
>> +	  Enable debugfs-based CXL protocol error injection. Writes to
>> +	  /sys/kernel/debug/cxl/aer_einj_inject inject CXL RAS protocol
>> +	  errors using the AER internal error inject interface.
>> +
>> +	  This is a debug/test facility. Say N for production kernels.
>> +
>> +	  If unsure say N.
>> +
>>  config CXL_ATL
>>  	def_bool y
>>  	depends on CXL_REGION
>> diff --git a/drivers/cxl/core/core.h b/drivers/cxl/core/core.h
>> index a55a4e409feda..91910d2bb5d39 100644
>> --- a/drivers/cxl/core/core.h
>> +++ b/drivers/cxl/core/core.h
>> @@ -182,6 +182,9 @@ static inline struct device *dport_to_host(struct cxl_dport *dport)
>>  		return port->uport_dev;
>>  	return &port->dev;
>>  }
>> +
>> +extern struct dentry *cxl_debugfs;
>> +
>>  #ifdef CONFIG_CXL_RAS
>>  void cxl_ras_init(void);
>>  void cxl_ras_exit(void);
>> @@ -244,4 +247,22 @@ int cxl_set_feature(struct cxl_mailbox *cxl_mbox, const uuid_t *feat_uuid,
>>  
>>  resource_size_t cxl_rcd_component_reg_phys(struct device *dev,
>>  					   struct cxl_dport *dport);
>> +
>> +#ifdef CONFIG_CXL_PROTO_AER_EINJ
>> +
>> +#define AER_REGISTER_SIZE 5
>> +#define RAS_REGISTER_SIZE (CXL_RAS_CAPABILITY_LENGTH / sizeof(u32))
>> +
>> +struct cxl_aer_einj {
>> +	int correctable;
>> +	bool is_rch;
>> +	struct mutex *lock;
>> +	struct device *dev;
>> +	u32 aer_registers[AER_REGISTER_SIZE];
>> +	u32 ras_registers[RAS_REGISTER_SIZE];
>> +};
>> +
>> +extern struct cxl_aer_einj cxl_aer_einj;
>> +#endif
>> +
>>  #endif /* __CXL_CORE_H__ */
>> diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
>> index a76f3ee05cba8..79657e5fddaac 100644
>> --- a/drivers/cxl/core/port.c
>> +++ b/drivers/cxl/core/port.c
>> @@ -2501,7 +2501,7 @@ const struct bus_type cxl_bus_type = {
>>  };
>>  EXPORT_SYMBOL_NS_GPL(cxl_bus_type, "CXL");
>>  
>> -static struct dentry *cxl_debugfs;
>> +struct dentry *cxl_debugfs;
>>  
>>  struct dentry *cxl_debugfs_create_dir(const char *dir)
>>  {
>> diff --git a/drivers/cxl/core/ras.c b/drivers/cxl/core/ras.c
>> index d77208af41e03..d41deea899d30 100644
>> --- a/drivers/cxl/core/ras.c
>> +++ b/drivers/cxl/core/ras.c
>> @@ -3,6 +3,7 @@
>>  
>>  #include <linux/pci.h>
>>  #include <linux/aer.h>
>> +#include <linux/debugfs.h>
>>  #include <cxl/event.h>
>>  #include <cxlmem.h>
>>  #include <cxlpci.h>
>> @@ -117,6 +118,195 @@ static void cxl_cper_prot_err_work_fn(struct work_struct *work)
>>  }
>>  static DECLARE_WORK(cxl_cper_prot_err_work, cxl_cper_prot_err_work_fn);
>>  
>> +#if IS_ENABLED(CONFIG_CXL_PROTO_AER_EINJ)
> 
> Can this be moved to a header file? Prefer to not introduce #ifdef in the C source.
> 

Yes, I will move to core.h. 

>> +
>> +static DEFINE_MUTEX(cxl_aer_einj_mutex);
>> +
>> +struct cxl_aer_einj cxl_aer_einj = {
>> +	.lock = &cxl_aer_einj_mutex,
>> +};
>> +
>> +static const char cxl_aer_einj_usage[] =
>> +	"ssss:bb:dd.f [UCE|CE] AER_STATUS RAS_STATUS [RCH]\n";
>> +
>> +static int cxl_aer_inject_error(struct pci_dev *pdev, bool correctable,
>> +				u32 aer_status, u32 ras_status)
>> +{
>> +	/* RCD errors are signaled as internal errors on the associated RCEC */
>> +	if (pci_pcie_type(pdev) == PCI_EXP_TYPE_RC_END) {
>> +		if (!pdev->rcec)
>> +			return -ENODEV;
>> +		pdev = pdev->rcec;
>> +	}
>> +
>> +	struct aer_error_inj einj = {
>> +		.bus = pdev->bus->number,
>> +		.dev = PCI_SLOT(pdev->devfn),
>> +		.fn = PCI_FUNC(pdev->devfn),
>> +		.domain = pci_domain_nr(pdev->bus),
>> +	};
>> +	int ret;
>> +	int aer_offset;
>> +	int ras_offset;
>> +
>> +	if (correctable) {
>> +		einj.cor_status = aer_status | PCI_ERR_COR_INTERNAL;
>> +		aer_offset = PCI_ERR_COR_STATUS / sizeof(u32);
>> +		ras_offset = CXL_RAS_CORRECTABLE_STATUS_OFFSET / sizeof(u32);
>> +	} else {
>> +		einj.uncor_status = aer_status | PCI_ERR_UNC_INTN;
>> +		aer_offset = PCI_ERR_UNCOR_STATUS / sizeof(u32);
>> +		ras_offset = CXL_RAS_UNCORRECTABLE_STATUS_OFFSET / sizeof(u32);
>> +	}
>> +
>> +	cxl_aer_einj.correctable = correctable;
>> +	cxl_aer_einj.aer_registers[aer_offset] = aer_status;
>> +	cxl_aer_einj.ras_registers[ras_offset] = ras_status;
>> +
>> +	ret = aer_inject(&einj);
>> +	if (ret) {
>> +		pr_err("cxl-einj: aer_inject failed: %d\n", ret);
>> +		return ret;
>> +	}
>> +
>> +	return 0;
>> +}
>> +
>> +static ssize_t cxl_aer_einj_write(struct file *file,
>> +				    const char __user *ubuf,
>> +				    size_t count, loff_t *ppos)
>> +{
>> +	char sbdf[16], severity[4], topology[4] = "";
>> +	unsigned int domain, bus, dev, fn;
>> +	u32 aer_status, ras_status;
>> +	struct cxl_dport *dport;
>> +	char buf[128];
>> +	int nargs;
>> +	int ret;
>> +
>> +	if (!capable(CAP_SYS_ADMIN))
>> +		return -EPERM;
>> +
>> +	if (count >= sizeof(buf)) {
>> +		pr_err("cxl-einj: input too long (%zu bytes, max %zu)\n", count, sizeof(buf) - 1);
>> +		return -EINVAL;
>> +	}
>> +
>> +	if (copy_from_user(buf, ubuf, count)) {
>> +		pr_err("cxl-einj: copy_from_user failed\n");
>> +		return -EFAULT;
>> +	}
>> +	buf[count] = '\0';
>> +
>> +	nargs = sscanf(buf, "%15s %3s %x %x %3s", sbdf, severity,
>> +		       &aer_status, &ras_status, topology);
>> +	if (nargs < 4) {
>> +		pr_err("cxl-einj: expected format: <SBDF> <UCE|CE> <aer_status> <ras_status>\n");
>> +		return -EINVAL;
>> +	}
>> +
>> +	if (nargs == 5 && strcmp(topology, "RCH") != 0)
>> +		return -EINVAL;
>> +
>> +	if (strcmp(severity, "UCE") != 0 && strcmp(severity, "CE") != 0) {
>> +		pr_err("cxl-einj: expected 'UCE' or 'CE', got '%s'\n", severity);
>> +		return -EINVAL;
>> +	}
>> +
>> +	if (sscanf(sbdf, "%x:%x:%x.%x", &domain, &bus, &dev, &fn) != 4) {
>> +		pr_err("cxl-einj: invalid SBDF format '%s', expected DDDD:BB:DD.F\n", sbdf);
>> +		return -EINVAL;
>> +	}
>> +
>> +	struct pci_dev *pdev __free(pci_dev_put) =
>> +		pci_get_domain_bus_and_slot(domain, bus, PCI_DEVFN(dev, fn));
>> +	if (!pdev) {
>> +		pr_err("cxl-einj: device %s not found\n", sbdf);
>> +		return -ENODEV;
>> +	}
>> +
>> +	guard(mutex)(cxl_aer_einj.lock);
>> +	cxl_aer_einj.dev = NULL;
>> +
>> +	struct cxl_port *port __free(put_cxl_port) = find_cxl_port_by_dev(&pdev->dev, &dport);
>> +	if (!port) {
>> +		dev_err(&pdev->dev, "cxl-einj: Failed to find CXL Port.\n");
>> +		return -ENODEV;
>> +	}
>> +
>> +	if (!to_ras_base(port, dport)) {
>> +		dev_err(&pdev->dev, "cxl-einj: RAS not initialized.\n");
>> +		return -ENODEV;
>> +	}
>> +
>> +	cxl_aer_einj.is_rch = (nargs == 5 && strcmp(topology, "RCH") == 0);
>> +	if (!cxl_aer_einj.is_rch)
>> +		pci_dev_get(pdev);
>> +	cxl_aer_einj.dev = cxl_aer_einj.is_rch ? pdev->dev.parent : &pdev->dev;
>> +	ret = cxl_aer_inject_error(pdev, strcmp(severity, "CE") == 0,
>> +				   aer_status, ras_status);
>> +	if (ret) {
>> +		if (!cxl_aer_einj.is_rch)
>> +			pci_dev_put(pdev);
>> +		cxl_aer_einj.dev = NULL;
>> +		pr_err("cxl-einj: injection failed for %s: %d\n", sbdf, ret);
>> +		return ret;
>> +	}
>> +
>> +	return count;
>> +}
>> +
>> +static ssize_t cxl_aer_einj_read(struct file *file, char __user *ubuf,
>> +				 size_t count, loff_t *ppos)
>> +{
>> +	return simple_read_from_buffer(ubuf, count, ppos,
>> +				       cxl_aer_einj_usage,
>> +				       sizeof(cxl_aer_einj_usage) - 1);
>> +}
>> +
>> +static const struct file_operations cxl_ras_error_fops = {
>> +	.owner		= THIS_MODULE,
>> +	.read		= cxl_aer_einj_read,
>> +	.write		= cxl_aer_einj_write,
>> +	.llseek		= default_llseek,
>> +};
>> +
>> +static void cxl_ras_create_debugfs(struct dentry *dir)
>> +{
>> +	debugfs_create_file("aer_einj_inject", 0600, dir, NULL,
>> +			    &cxl_ras_error_fops);
>> +}
>> +
>> +static void __iomem *to_einj_ras_base(struct cxl_port *port, struct cxl_dport *dport)
>> +{
>> +	if (dport) {
>> +		if (cxl_aer_einj.is_rch) {
>> +			if (cxl_aer_einj.dev == dport->dport_dev) {
>> +				cxl_aer_einj.dev = NULL;
>> +				return (__force void __iomem *)cxl_aer_einj.ras_registers;
>> +			}
>> +		} else {
>> +			if (cxl_aer_einj.dev == dport->dport_dev) {
>> +				pci_dev_put(to_pci_dev(cxl_aer_einj.dev));
>> +				cxl_aer_einj.dev = NULL;
>> +				return (__force void __iomem *)cxl_aer_einj.ras_registers;
>> +			}
>> +		}
>> +	} else if (!cxl_aer_einj.is_rch) {
>> +		struct device *dev = is_cxl_endpoint(port) ?
>> +			port->uport_dev->parent : port->uport_dev;
>> +
>> +		if (dev_is_pci(dev) && cxl_aer_einj.dev == dev) {
>> +			pci_dev_put(to_pci_dev(cxl_aer_einj.dev));
>> +			cxl_aer_einj.dev = NULL;
>> +			return (__force void __iomem *)cxl_aer_einj.ras_registers;
>> +		}
>> +	}
>> +
>> +	return NULL;
>> +}
>> +#endif
>> +
>>  static void cxl_unmask_proto_interrupts(struct device *dev)
>>  {
>>  	struct pci_dev *pdev;
>> @@ -238,6 +428,14 @@ void __iomem *to_ras_base(struct cxl_port *port, struct cxl_dport *dport)
>>  	if (!port)
>>  		return NULL;
>>  
>> +#if IS_ENABLED(CONFIG_CXL_PROTO_AER_EINJ)
> 
> I think you can do something like below instead:
> 
> 	if (IS_ENABLED(CONFIG_CXL_PROTO_AER_EINJ))
> 
> DJ
> 

Good idea. Thanks for pointing this out.

Terry

[snip]