PCI/AER: Add sysfs attributes for log ratelimits

Allow userspace to read/write log ratelimits per device (including
enable/disable). Create aer/ sysfs directory to store them and any
future AER configs.

The new sysfs files are:

  /sys/bus/pci/devices/*/aer/correctable_ratelimit_burst
  /sys/bus/pci/devices/*/aer/correctable_ratelimit_interval_ms
  /sys/bus/pci/devices/*/aer/nonfatal_ratelimit_burst
  /sys/bus/pci/devices/*/aer/nonfatal_ratelimit_interval_ms

The default values are ratelimit_burst=10, ratelimit_interval_ms=5000, so
if we try to emit more than 10 messages in a 5 second period, some are
suppressed.

Update AER sysfs ABI filename to reflect the broader scope of AER sysfs
attributes (e.g. stats and ratelimits).

  Documentation/ABI/testing/sysfs-bus-pci-devices-aer_stats ->
    sysfs-bus-pci-devices-aer

Tested using aer-inject[1]. Configured correctable log ratelimit to 5.
Sent 6 AER errors. Observed 5 errors logged while AER stats
(cat /sys/bus/pci/devices/<dev>/aer_dev_correctable) shows 6.

Disabled ratelimiting and sent 6 more AER errors. Observed all 6 errors
logged and accounted in AER stats (12 total errors).

[1] https://git.kernel.org/pub/scm/linux/kernel/git/gong.chen/aer-inject.git

[bhelgaas: note fatal errors are not ratelimited, "aer_report" ->
"aer_info", replace ratelimit_log_enable toggle with *_ratelimit_interval_ms]

Signed-off-by: Karolina Stolarek <karolina.stolarek@oracle.com>
Signed-off-by: Jon Pan-Doh <pandoh@google.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Link: https://patch.msgid.link/20250522232339.1525671-21-helgaas@kernel.org

Documentation/ABI/testing/sysfs-bus-pci-devices-aer

@@ -117,3 +117,47 @@ Date:		July 2018
 KernelVersion:	4.19.0
 Contact:	linux-pci@vger.kernel.org, rajatja@google.com
 Description:	Total number of ERR_NONFATAL messages reported to rootport.
+
+PCIe AER ratelimits
+-------------------
+
+These attributes show up under all the devices that are AER capable.
+They represent configurable ratelimits of logs per error type.
+
+See Documentation/PCI/pcieaer-howto.rst for more info on ratelimits.
+
+What:		/sys/bus/pci/devices/<dev>/aer/correctable_ratelimit_interval_ms
+Date:		May 2025
+KernelVersion:	6.16.0
+Contact:	linux-pci@vger.kernel.org
+Description:	Writing 0 disables AER correctable error log ratelimiting.
+		Writing a positive value sets the ratelimit interval in ms.
+		Default is DEFAULT_RATELIMIT_INTERVAL (5000 ms).
+
+What:		/sys/bus/pci/devices/<dev>/aer/correctable_ratelimit_burst
+Date:		May 2025
+KernelVersion:	6.16.0
+Contact:	linux-pci@vger.kernel.org
+Description:	Ratelimit burst for correctable error logs. Writing a value
+		changes the number of errors (burst) allowed per interval
+		before ratelimiting. Reading gets the current ratelimit
+		burst. Default is DEFAULT_RATELIMIT_BURST (10).
+
+What:		/sys/bus/pci/devices/<dev>/aer/nonfatal_ratelimit_interval_ms
+Date:		May 2025
+KernelVersion:	6.16.0
+Contact:	linux-pci@vger.kernel.org
+Description:	Writing 0 disables AER non-fatal uncorrectable error log
+		ratelimiting. Writing a positive value sets the ratelimit
+		interval in ms. Default is DEFAULT_RATELIMIT_INTERVAL
+		(5000 ms).
+
+What:		/sys/bus/pci/devices/<dev>/aer/nonfatal_ratelimit_burst
+Date:		May 2025
+KernelVersion:	6.16.0
+Contact:	linux-pci@vger.kernel.org
+Description:	Ratelimit burst for non-fatal uncorrectable error logs.
+		Writing a value changes the number of errors (burst)
+		allowed per interval before ratelimiting. Reading gets the
+		current ratelimit burst. Default is DEFAULT_RATELIMIT_BURST
+		(10).

Documentation/PCI/pcieaer-howto.rst

@@ -97,12 +97,15 @@ DPC errors, are not ratelimited.
 AER uses the default ratelimit of DEFAULT_RATELIMIT_BURST (10 events) over
 DEFAULT_RATELIMIT_INTERVAL (5 seconds).
 
+Ratelimits are exposed in the form of sysfs attributes and configurable.
+See Documentation/ABI/testing/sysfs-bus-pci-devices-aer.
+
 AER Statistics / Counters
 -------------------------
 
 When PCIe AER errors are captured, the counters / statistics are also exposed
 in the form of sysfs attributes which are documented at
-Documentation/ABI/testing/sysfs-bus-pci-devices-aer_stats
+Documentation/ABI/testing/sysfs-bus-pci-devices-aer.
 
 Developer Guide
 ===============

drivers/pci/pci-sysfs.c

@@ -1805,6 +1805,7 @@ const struct attribute_group *pci_dev_attr_groups[] = {
 	&pcie_dev_attr_group,
 #ifdef CONFIG_PCIEAER
 	&aer_stats_attr_group,
+	&aer_attr_group,
 #endif
 #ifdef CONFIG_PCIEASPM
 	&aspm_ctrl_attr_group,

drivers/pci/pci.h

@@ -965,6 +965,7 @@ void pci_no_aer(void);
 void pci_aer_init(struct pci_dev *dev);
 void pci_aer_exit(struct pci_dev *dev);
 extern const struct attribute_group aer_stats_attr_group;
+extern const struct attribute_group aer_attr_group;
 void pci_aer_clear_fatal_status(struct pci_dev *dev);
 int pci_aer_clear_status(struct pci_dev *dev);
 int pci_aer_raw_clear_status(struct pci_dev *dev);

drivers/pci/pcie/aer.c

@@ -627,6 +627,111 @@ const struct attribute_group aer_stats_attr_group = {
 	.is_visible = aer_stats_attrs_are_visible,
 };
 
+/*
+ * Ratelimit interval
+ * <=0: disabled with ratelimit.interval = 0
+ * >0: enabled with ratelimit.interval in ms
+ */
+#define aer_ratelimit_interval_attr(name, ratelimit)			\
+	static ssize_t							\
+	name##_show(struct device *dev, struct device_attribute *attr,	\
+					 char *buf)			\
+	{								\
+		struct pci_dev *pdev = to_pci_dev(dev);			\
+									\
+		return sysfs_emit(buf, "%d\n",				\
+				  pdev->aer_info->ratelimit.interval);	\
+	}								\
+									\
+	static ssize_t							\
+	name##_store(struct device *dev, struct device_attribute *attr, \
+		     const char *buf, size_t count) 			\
+	{								\
+		struct pci_dev *pdev = to_pci_dev(dev);			\
+		int interval;						\
+									\
+		if (!capable(CAP_SYS_ADMIN))				\
+			return -EPERM;					\
+									\
+		if (kstrtoint(buf, 0, &interval) < 0)			\
+			return -EINVAL;					\
+									\
+		if (interval <= 0)					\
+			interval = 0;					\
+		else							\
+			interval = msecs_to_jiffies(interval); 		\
+									\
+		pdev->aer_info->ratelimit.interval = interval;		\
+									\
+		return count;						\
+	}								\
+	static DEVICE_ATTR_RW(name);
+
+#define aer_ratelimit_burst_attr(name, ratelimit)			\
+	static ssize_t							\
+	name##_show(struct device *dev, struct device_attribute *attr,	\
+		    char *buf)						\
+	{								\
+		struct pci_dev *pdev = to_pci_dev(dev);			\
+									\
+		return sysfs_emit(buf, "%d\n",				\
+				  pdev->aer_info->ratelimit.burst);	\
+	}								\
+									\
+	static ssize_t							\
+	name##_store(struct device *dev, struct device_attribute *attr,	\
+		     const char *buf, size_t count)			\
+	{								\
+		struct pci_dev *pdev = to_pci_dev(dev);			\
+		int burst;						\
+									\
+		if (!capable(CAP_SYS_ADMIN))				\
+			return -EPERM;					\
+									\
+		if (kstrtoint(buf, 0, &burst) < 0)			\
+			return -EINVAL;					\
+									\
+		pdev->aer_info->ratelimit.burst = burst;		\
+									\
+		return count;						\
+	}								\
+	static DEVICE_ATTR_RW(name);
+
+#define aer_ratelimit_attrs(name)					\
+	aer_ratelimit_interval_attr(name##_ratelimit_interval_ms,	\
+				    name##_ratelimit)			\
+	aer_ratelimit_burst_attr(name##_ratelimit_burst,		\
+				 name##_ratelimit)
+
+aer_ratelimit_attrs(correctable)
+aer_ratelimit_attrs(nonfatal)
+
+static struct attribute *aer_attrs[] = {
+	&dev_attr_correctable_ratelimit_interval_ms.attr,
+	&dev_attr_correctable_ratelimit_burst.attr,
+	&dev_attr_nonfatal_ratelimit_interval_ms.attr,
+	&dev_attr_nonfatal_ratelimit_burst.attr,
+	NULL
+};
+
+static umode_t aer_attrs_are_visible(struct kobject *kobj,
+				     struct attribute *a, int n)
+{
+	struct device *dev = kobj_to_dev(kobj);
+	struct pci_dev *pdev = to_pci_dev(dev);
+
+	if (!pdev->aer_info)
+		return 0;
+
+	return a->mode;
+}
+
+const struct attribute_group aer_attr_group = {
+	.name = "aer",
+	.attrs = aer_attrs,
+	.is_visible = aer_attrs_are_visible,
+};
+
 static void pci_dev_aer_stats_incr(struct pci_dev *pdev,
 				   struct aer_err_info *info)
 {