[PATCH v3 7/8] PCI/AER: Add sysfs attributes for log ratelimits

[Jon Pan-Doh <pandoh@google.com>]

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

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

Signed-off-by: Karolina Stolarek <karolina.stolarek@oracle.com>
Signed-off-by: Jon Pan-Doh <pandoh@google.com>
---
 .../testing/sysfs-bus-pci-devices-aer_stats   | 34 +++++++
 Documentation/PCI/pcieaer-howto.rst           |  3 +
 drivers/pci/pci-sysfs.c                       |  1 +
 drivers/pci/pci.h                             |  1 +
 drivers/pci/pcie/aer.c                        | 93 +++++++++++++++++++
 5 files changed, 132 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-bus-pci-devices-aer_stats b/Documentation/ABI/testing/sysfs-bus-pci-devices-aer_stats
index d1f67bb81d5d..4561653fdbde 100644
--- a/Documentation/ABI/testing/sysfs-bus-pci-devices-aer_stats
+++ b/Documentation/ABI/testing/sysfs-bus-pci-devices-aer_stats
@@ -117,3 +117,37 @@ 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/ratelimit_log_enable
+Date:		March 2025
+KernelVersion:	6.15.0
+Contact:	linux-pci@vger.kernel.org, pandoh@google.com
+Description:	Writing 1/0 enables/disables AER log ratelimiting. Reading
+		gets whether or not AER is currently enabled. Enabled by
+		default.
+
+What:		/sys/bus/pci/devices/<dev>/aer/ratelimit_in_5secs_cor_log
+Date:		March 2025
+KernelVersion:	6.15.0
+Contact:	linux-pci@vger.kernel.org, pandoh@google.com
+Description:	Ratelimit burst for correctable error logs. Writing a value
+		changes the number of errors (burst) allowed per interval
+		(5 second window) before ratelimiting. Reading gets the
+		current ratelimit burst.
+
+What:		/sys/bus/pci/devices/<dev>/aer/ratelimit_in_5secs_uncor_log
+Date:		March 2025
+KernelVersion:	6.15.0
+Contact:	linux-pci@vger.kernel.org, pandoh@google.com
+Description:	Ratelimit burst for uncorrectable error logs. Writing a
+		value changes the number of errors (burst) allowed per
+		interval (5 second window) before ratelimiting. Reading
+		gets the current ratelimit burst.
diff --git a/Documentation/PCI/pcieaer-howto.rst b/Documentation/PCI/pcieaer-howto.rst
index 896d2a232a90..b45a2e18d1cf 100644
--- a/Documentation/PCI/pcieaer-howto.rst
+++ b/Documentation/PCI/pcieaer-howto.rst
@@ -96,6 +96,9 @@ type (correctable vs. uncorrectable).
 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_stats.
+
 AER Statistics / Counters
 -------------------------
 
diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index b46ce1a2c554..16de3093294e 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -1801,6 +1801,7 @@ 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,
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index 9d63d32f041c..34633fe12201 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -889,6 +889,7 @@ 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);
diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
index 0bd20c4993d4..13227a94c9f9 100644
--- a/drivers/pci/pcie/aer.c
+++ b/drivers/pci/pcie/aer.c
@@ -631,6 +631,99 @@ const struct attribute_group aer_stats_attr_group = {
 	.is_visible = aer_stats_attrs_are_visible,
 };
 
+/*
+ * Ratelimit enable toggle uses interval value of
+ * 0: disabled
+ * DEFAULT_RATELIMIT_INTERVAL: enabled
+ */
+static ssize_t ratelimit_log_enable_show(struct device *dev,
+					 struct device_attribute *attr,
+					 char *buf)
+{
+	struct pci_dev *pdev = to_pci_dev(dev);
+	bool enable = pdev->aer_report->cor_log_ratelimit.interval != 0;
+
+	return sysfs_emit(buf, "%d\n", enable);
+}
+
+static ssize_t ratelimit_log_enable_store(struct device *dev,
+					  struct device_attribute *attr,
+					  const char *buf, size_t count)
+{
+	struct pci_dev *pdev = to_pci_dev(dev);
+	bool enable;
+	int interval;
+
+	if (kstrtobool(buf, &enable) < 0)
+		return -EINVAL;
+
+	if (enable)
+		interval = DEFAULT_RATELIMIT_INTERVAL;
+	else
+		interval = 0;
+
+	pdev->aer_report->cor_log_ratelimit.interval = interval;
+	pdev->aer_report->uncor_log_ratelimit.interval = interval;
+	return count;
+}
+static DEVICE_ATTR_RW(ratelimit_log_enable);
+
+/*
+ * Ratelimits are doubled as a given error produces 2 logs (root port
+ * and endpoint) that should be under same ratelimit.
+ */
+#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_report->ratelimit.burst / 2);	\
+}									\
+									\
+	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 (kstrtoint(buf, 0, &burst) < 0)				\
+		return -EINVAL;						\
+									\
+	pdev->aer_report->ratelimit.burst = burst * 2;			\
+	return count;							\
+}									\
+static DEVICE_ATTR_RW(name)
+
+aer_ratelimit_burst_attr(ratelimit_in_5secs_cor_log, cor_log_ratelimit);
+aer_ratelimit_burst_attr(ratelimit_in_5secs_uncor_log, uncor_log_ratelimit);
+
+static struct attribute *aer_attrs[] = {
+	&dev_attr_ratelimit_log_enable.attr,
+	&dev_attr_ratelimit_in_5secs_cor_log.attr,
+	&dev_attr_ratelimit_in_5secs_uncor_log.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_report)
+		return 0;
+	return a->mode;
+}
+
+const struct attribute_group aer_attr_group = {
+	.name = "aer",
+	.attrs = aer_attrs,
+	.is_visible = aer_attrs_are_visible,
+};
+
 void pci_dev_aer_stats_incr(struct pci_dev *pdev, struct aer_err_info *info)
 {
 	unsigned long status = info->status & ~info->mask;
-- 
2.49.0.rc1.451.g8f38331e32-goog