[PATCH v2 7/8] PCI/AER: Add AER sysfs attributes for log ratelimits

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

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

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

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

Signed-off-by: Jon Pan-Doh <pandoh@google.com>
---
 .../testing/sysfs-bus-pci-devices-aer_stats   | 20 +++++++
 Documentation/PCI/pcieaer-howto.rst           |  3 ++
 drivers/pci/pci-sysfs.c                       |  1 +
 drivers/pci/pci.h                             |  1 +
 drivers/pci/pcie/aer.c                        | 52 +++++++++++++++++++
 5 files changed, 77 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..c1221614c079 100644
--- a/Documentation/ABI/testing/sysfs-bus-pci-devices-aer_stats
+++ b/Documentation/ABI/testing/sysfs-bus-pci-devices-aer_stats
@@ -117,3 +117,23 @@ 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.
+Provides configurable ratelimits of logs/irq per error type. Writing a
+nonzero value changes the number of errors (burst) allowed per 5 second
+window before ratelimiting. Reading gets the current ratelimits.
+
+What:		/sys/bus/pci/devices/<dev>/aer/ratelimit_cor_log
+Date:		March 2025
+KernelVersion:	6.15.0
+Contact:	linux-pci@vger.kernel.org, pandoh@google.com
+Description:	Log ratelimit for correctable errors.
+
+What:		/sys/bus/pci/devices/<dev>/aer/ratelimit_uncor_log
+Date:		March 2025
+KernelVersion:	6.15.0
+Contact:	linux-pci@vger.kernel.org, pandoh@google.com
+Description:	Log ratelimit for uncorrectable errors.
diff --git a/Documentation/PCI/pcieaer-howto.rst b/Documentation/PCI/pcieaer-howto.rst
index 167c0b277b62..ab5b0f232204 100644
--- a/Documentation/PCI/pcieaer-howto.rst
+++ b/Documentation/PCI/pcieaer-howto.rst
@@ -93,6 +93,9 @@ spammy devices from flooding the console and stalling execution. Set the
 default ratelimit to DEFAULT_RATELIMIT_BURST over
 DEFAULT_RATELIMIT_INTERVAL (10 per 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 26104aee06c0..26d30a99c48b 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -887,6 +887,7 @@ 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 c5b5381e2930..1237faee6542 100644
--- a/drivers/pci/pcie/aer.c
+++ b/drivers/pci/pcie/aer.c
@@ -626,6 +626,58 @@ const struct attribute_group aer_stats_attr_group = {
 	.is_visible = aer_stats_attrs_are_visible,
 };
 
+#define aer_ratelimit_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, "%u errors every %u seconds\n",		\
+			  pdev->aer_report->ratelimit.burst,		\
+			  pdev->aer_report->ratelimit.interval / HZ);	\
+}									\
+									\
+	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;			\
+	return count;							\
+}									\
+static DEVICE_ATTR_RW(name)
+
+aer_ratelimit_attr(ratelimit_cor_log, cor_log_ratelimit);
+aer_ratelimit_attr(ratelimit_uncor_log, uncor_log_ratelimit);
+
+static struct attribute *aer_attrs[] __ro_after_init = {
+	&dev_attr_ratelimit_cor_log.attr,
+	&dev_attr_ratelimit_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;
-- 
2.48.1.601.g30ceb7b040-goog