[PATCH v6 14/16] PCI/AER: Introduce ratelimit for error logs

Bjorn Helgaas
2025-05-19T21:37:13Z

From: Jon Pan-Doh <pandoh@google.com>

Spammy devices can flood kernel logs with AER errors and slow/stall
execution. Add per-device ratelimits for AER correctable and uncorrectable
errors that use the kernel defaults (10 per 5s).

There are two AER logging entry points:

- aer_print_error() is used by DPC and native AER

- pci_print_aer() is used by GHES and CXL

The native AER aer_print_error() case includes a loop that may log details
from multiple devices. This is ratelimited by the union of ratelimits for
these devices, set by add_error_device(), which collects the devices. If
no such device is found, the Error Source message is ratelimited by the
Root Port or RCEC that received the ERR_* message.

The DPC aer_print_error() case is currently not ratelimited.

The GHES and CXL pci_print_aer() cases are ratelimited by the Error Source
device.

Sargun at Meta reported internally that a flood of AER errors causes RCU
CPU stall warnings and CSD-lock warnings.

Tested using aer-inject[1]. Sent 11 AER errors. Observed 10 errors logged
while AER stats (cat /sys/bus/pci/devices/<dev>/aer_dev_correctable) show
true count of 11.

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

[bhelgaas: commit log, factor out trace_aer_event() and aer_print_rp_info()
changes to previous patches, collect single aer_err_info.ratelimit as union
of ratelimits of all error source devices]
Link: https://lore.kernel.org/r/20250321015806.954866-7-pandoh@google.com
Reported-by: Sargun Dhillon <sargun@meta.com>
Signed-off-by: Jon Pan-Doh <pandoh@google.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
---
drivers/pci/pci.h | 3 ++-
drivers/pci/pcie/aer.c | 49 ++++++++++++++++++++++++++++++++++++------
drivers/pci/pcie/dpc.c | 1 +
3 files changed, 46 insertions(+), 7 deletions(-)

diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index 705f9ef58acc..65c466279ade 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -593,7 +593,8 @@ struct aer_err_info {
unsigned int id:16;

unsigned int severity:2; /* 0:NONFATAL | 1:FATAL | 2:COR */
- unsigned int __pad1:5;
+ unsigned int ratelimit:1; /* 0=skip, 1=print */
+ unsigned int __pad1:4;
unsigned int multi_error_valid:1;

unsigned int first_error:5;
diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
index da62032bf024..c335e0bb9f51 100644
--- a/drivers/pci/pcie/aer.c
+++ b/drivers/pci/pcie/aer.c
@@ -28,6 +28,7 @@
#include <linux/interrupt.h>
#include <linux/delay.h>
#include <linux/kfifo.h>
+#include <linux/ratelimit.h>
#include <linux/slab.h>
#include <acpi/apei.h>
#include <acpi/ghes.h>
@@ -88,6 +89,10 @@ struct aer_report {
u64 rootport_total_cor_errs;
u64 rootport_total_fatal_errs;
u64 rootport_total_nonfatal_errs;
+
+ /* Ratelimits for errors */
+ struct ratelimit_state cor_log_ratelimit;
+ struct ratelimit_state uncor_log_ratelimit;
};

#define AER_LOG_TLP_MASKS (PCI_ERR_UNC_POISON_TLP| \
@@ -379,6 +384,11 @@ void pci_aer_init(struct pci_dev *dev)

dev->aer_report = kzalloc(sizeof(*dev->aer_report), GFP_KERNEL);

+ ratelimit_state_init(&dev->aer_report->cor_log_ratelimit,
+ DEFAULT_RATELIMIT_INTERVAL, DEFAULT_RATELIMIT_BURST);
+ ratelimit_state_init(&dev->aer_report->uncor_log_ratelimit,
+ DEFAULT_RATELIMIT_INTERVAL, DEFAULT_RATELIMIT_BURST);
+
/*
* We save/restore PCI_ERR_UNCOR_MASK, PCI_ERR_UNCOR_SEVER,
* PCI_ERR_COR_MASK, and PCI_ERR_CAP. Root and Root Complex Event
@@ -672,6 +682,18 @@ static void pci_rootport_aer_stats_incr(struct pci_dev *pdev,
}
}

+static int aer_ratelimit(struct pci_dev *dev, unsigned int severity)
+{
+ struct ratelimit_state *ratelimit;
+
+ if (severity == AER_CORRECTABLE)
+ ratelimit = &dev->aer_report->cor_log_ratelimit;
+ else
+ ratelimit = &dev->aer_report->uncor_log_ratelimit;
+
+ return __ratelimit(ratelimit);
+}
+
static void __aer_print_error(struct pci_dev *dev, struct aer_err_info *info)
{
const char **strings;
@@ -715,6 +737,9 @@ void aer_print_error(struct pci_dev *dev, struct aer_err_info *info)

pci_dev_aer_stats_incr(dev, info);

+ if (!info->ratelimit)
+ return;
+
if (!info->status) {
pci_err(dev, "PCIe Bus Error: severity=%s, type=Inaccessible, (Unregistered Agent ID)\n",
aer_error_severity_string[info->severity]);
@@ -785,6 +810,9 @@ void pci_print_aer(struct pci_dev *dev, int aer_severity,

pci_dev_aer_stats_incr(dev, &info);

+ if (!aer_ratelimit(dev, info.severity))
+ return;
+
layer = AER_GET_LAYER_ERROR(aer_severity, status);
agent = AER_GET_AGENT(aer_severity, status);

@@ -815,8 +843,14 @@ EXPORT_SYMBOL_NS_GPL(pci_print_aer, "CXL");
*/
static int add_error_device(struct aer_err_info *e_info, struct pci_dev *dev)
{
+ /*
+ * Ratelimit AER log messages. Generally we add the Error Source
+ * device, but there are is_error_source() cases that can result in
+ * multiple devices being added here, so we OR them all together.
+ */
if (e_info->error_dev_num < AER_MAX_MULTI_ERR_DEVICES) {
e_info->dev[e_info->error_dev_num] = pci_dev_get(dev);
+ e_info->ratelimit |= aer_ratelimit(dev, e_info->severity);
e_info->error_dev_num++;
return 0;
}
@@ -914,7 +948,7 @@ static int find_device_iter(struct pci_dev *dev, void *data)
* e_info->error_dev_num and e_info->dev[], based on the given information.
*/
static bool find_source_device(struct pci_dev *parent,
- struct aer_err_info *e_info)
+ struct aer_err_info *e_info)
{
struct pci_dev *dev = parent;
int result;
@@ -935,10 +969,12 @@ static bool find_source_device(struct pci_dev *parent,
/*
* If we didn't find any devices with errors logged in the AER
* Capability, just print the Error Source ID from the Root Port or
- * RCEC that received an ERR_* Message.
+ * RCEC that received an ERR_* Message, ratelimited by the RP or
+ * RCEC.
*/
if (!e_info->error_dev_num) {
- aer_print_source(parent, e_info, " (no details found)");
+ if (aer_ratelimit(parent, e_info->severity))
+ aer_print_source(parent, e_info, " (no details found)");
return false;
}
return true;
@@ -1147,9 +1183,10 @@ static void aer_recover_work_func(struct work_struct *work)
pdev = pci_get_domain_bus_and_slot(entry.domain, entry.bus,
entry.devfn);
if (!pdev) {
- pr_err("no pci_dev for %04x:%02x:%02x.%x\n",
- entry.domain, entry.bus,
- PCI_SLOT(entry.devfn), PCI_FUNC(entry.devfn));
+ pr_err_ratelimited("%04x:%02x:%02x.%x: no pci_dev found\n",
+ entry.domain, entry.bus,
+ PCI_SLOT(entry.devfn),
+ PCI_FUNC(entry.devfn));
continue;
}
pci_print_aer(pdev, entry.severity, entry.regs);
diff --git a/drivers/pci/pcie/dpc.c b/drivers/pci/pcie/dpc.c
index 34af0ea45c0d..597df7790f36 100644
--- a/drivers/pci/pcie/dpc.c
+++ b/drivers/pci/pcie/dpc.c
@@ -301,6 +301,7 @@ void dpc_process_error(struct pci_dev *pdev)
else if (reason == PCI_EXP_DPC_STATUS_TRIGGER_RSN_UNCOR &&
dpc_get_aer_uncorrect_severity(pdev, &info) &&
aer_get_device_error_info(pdev, &info)) {
+ info.ratelimit = 1; /* no ratelimiting */
aer_print_error(pdev, &info);
pci_aer_clear_nonfatal_status(pdev);
pci_aer_clear_fatal_status(pdev);
--
2.43.0