[PATCH 6/8] PCI/AER: Add AER sysfs attributes for ratelimits

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

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

Tested using aer-inject[1] tool. Configured correctable log/irq ratelimits
to 5/10 respectively. Sent 12 AER errors. Observed 5 errors logged while
AER stats (cat /sys/bus/pci/devices/<dev>/aer_dev_correctable) shows 11
(1 masked).

Before: CEMsk: BadTLP-
After:  CEMsk: BadTLP+.

[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   | 32 +++++++++++
 Documentation/PCI/pcieaer-howto.rst           |  4 +-
 drivers/pci/pci-sysfs.c                       |  1 +
 drivers/pci/pci.h                             |  1 +
 drivers/pci/pcie/aer.c                        | 56 +++++++++++++++++++
 5 files changed, 93 insertions(+), 1 deletion(-)

diff --git a/Documentation/ABI/testing/sysfs-bus-pci-devices-aer_stats b/Documentation/ABI/testing/sysfs-bus-pci-devices-aer_stats
index d1f67bb81d5d..c680a53af0f4 100644
--- a/Documentation/ABI/testing/sysfs-bus-pci-devices-aer_stats
+++ b/Documentation/ABI/testing/sysfs-bus-pci-devices-aer_stats
@@ -117,3 +117,35 @@ 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_irq
+Date:		Jan 2025
+KernelVersion:	6.14.0
+Contact:	linux-pci@vger.kernel.org, pandoh@google.com
+Description:	IRQ ratelimit for correctable errors.
+
+What:		/sys/bus/pci/devices/<dev>/aer/ratelimit_uncor_irq
+Date:		Jan 2025
+KernelVersion:	6.14.0
+Contact:	linux-pci@vger.kernel.org, pandoh@google.com
+Description:	IRQ ratelimit for uncorrectable errors.
+
+What:		/sys/bus/pci/devices/<dev>/aer/ratelimit_cor_log
+Date:		Jan 2025
+KernelVersion:	6.14.0
+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:		Jan 2025
+KernelVersion:	6.14.0
+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 d41272504b18..4d5b0638f120 100644
--- a/Documentation/PCI/pcieaer-howto.rst
+++ b/Documentation/PCI/pcieaer-howto.rst
@@ -89,7 +89,9 @@ AER Ratelimits
 -------------------------
 
 Errors, both at log and IRQ level, are ratelimited per device and error type.
-This prevents spammy devices from stalling execution.
+This prevents spammy devices from stalling execution. 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 7679d75d71e5..41acb6713e2d 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -1693,6 +1693,7 @@ 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 2e40fc63ba31..9d0272a890ef 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -881,6 +881,7 @@ 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 1db70ae87f52..e48e2951baae 100644
--- a/drivers/pci/pcie/aer.c
+++ b/drivers/pci/pcie/aer.c
@@ -630,6 +630,62 @@ 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_info->ratelimit.burst,		\
+			  pdev->aer_info->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_info->ratelimit.burst = burst;			\
+	return count;							\
+}									\
+static DEVICE_ATTR_RW(name)
+
+aer_ratelimit_attr(ratelimit_cor_irq, cor_irq_ratelimit);
+aer_ratelimit_attr(ratelimit_uncor_irq, uncor_irq_ratelimit);
+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_irq.attr,
+	&dev_attr_ratelimit_uncor_irq.attr,
+	&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_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)
 {
-- 
2.48.0.rc2.279.g1de40edade-goog