[PATCH v9 1/2] PCI: trace: Add a generic RAS tracepoint for hotplug event

Shuai Xue
2025-07-23T03:31:32Z

Hotplug events are critical indicators for analyzing hardware health,
and surprise link downs can significantly impact system performance and
reliability.

Define a new TRACING_SYSTEM named "pci", add a generic RAS tracepoint
for hotplug event to help health checks. Add enum pci_hotplug_event in
include/uapi/linux/pci.h so applications like rasdaemon can register
tracepoint event handlers for it.

The output is like below:

$ echo 1 > /sys/kernel/debug/tracing/events/pci/pci_hp_event/enable
$ cat /sys/kernel/debug/tracing/trace_pipe
<...>-206 [001] ..... 40.373870: pci_hp_event: 0000:00:02.0 slot:10, event:LINK_DOWN

<...>-206 [001] ..... 40.374871: pci_hp_event: 0000:00:02.0 slot:10, event:CARD_NOT_PRESENT

Suggested-by: Lukas Wunner <lukas@wunner.de>
Suggested-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Shuai Xue <xueshuai@linux.alibaba.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Lukas Wunner <lukas@wunner.de>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
---
drivers/pci/hotplug/pciehp_ctrl.c | 33 +++++++++++++---
include/trace/events/pci.h | 63 +++++++++++++++++++++++++++++++
include/uapi/linux/pci.h | 7 ++++
3 files changed, 97 insertions(+), 6 deletions(-)
create mode 100644 include/trace/events/pci.h

diff --git a/drivers/pci/hotplug/pciehp_ctrl.c b/drivers/pci/hotplug/pciehp_ctrl.c
index bcc938d4420f..d241f270c8de 100644
--- a/drivers/pci/hotplug/pciehp_ctrl.c
+++ b/drivers/pci/hotplug/pciehp_ctrl.c
@@ -20,6 +20,9 @@
#include <linux/pm_runtime.h>
#include <linux/pci.h>

+#define CREATE_TRACE_POINTS
+#include <trace/events/pci.h>
+
#include "../pci.h"
#include "pciehp.h"

@@ -244,12 +247,20 @@ void pciehp_handle_presence_or_link_change(struct controller *ctrl, u32 events)
case ON_STATE:
ctrl->state = POWEROFF_STATE;
mutex_unlock(&ctrl->state_lock);
- if (events & PCI_EXP_SLTSTA_DLLSC)
+ if (events & PCI_EXP_SLTSTA_DLLSC) {
ctrl_info(ctrl, "Slot(%s): Link Down\n",
slot_name(ctrl));
- if (events & PCI_EXP_SLTSTA_PDC)
+ trace_pci_hp_event(pci_name(ctrl->pcie->port),
+ slot_name(ctrl),
+ PCI_HOTPLUG_LINK_DOWN);
+ }
+ if (events & PCI_EXP_SLTSTA_PDC) {
ctrl_info(ctrl, "Slot(%s): Card not present\n",
slot_name(ctrl));
+ trace_pci_hp_event(pci_name(ctrl->pcie->port),
+ slot_name(ctrl),
+ PCI_HOTPLUG_CARD_NOT_PRESENT);
+ }
pciehp_disable_slot(ctrl, SURPRISE_REMOVAL);
break;
default:
@@ -269,6 +280,9 @@ void pciehp_handle_presence_or_link_change(struct controller *ctrl, u32 events)
INDICATOR_NOOP);
ctrl_info(ctrl, "Slot(%s): Card not present\n",
slot_name(ctrl));
+ trace_pci_hp_event(pci_name(ctrl->pcie->port),
+ slot_name(ctrl),
+ PCI_HOTPLUG_CARD_NOT_PRESENT);
}
mutex_unlock(&ctrl->state_lock);
return;
@@ -281,12 +295,19 @@ void pciehp_handle_presence_or_link_change(struct controller *ctrl, u32 events)
case OFF_STATE:
ctrl->state = POWERON_STATE;
mutex_unlock(&ctrl->state_lock);
- if (present)
+ if (present) {
ctrl_info(ctrl, "Slot(%s): Card present\n",
slot_name(ctrl));
- if (link_active)
- ctrl_info(ctrl, "Slot(%s): Link Up\n",
- slot_name(ctrl));
+ trace_pci_hp_event(pci_name(ctrl->pcie->port),
+ slot_name(ctrl),
+ PCI_HOTPLUG_CARD_PRESENT);
+ }
+ if (link_active) {
+ ctrl_info(ctrl, "Slot(%s): Link Up\n", slot_name(ctrl));
+ trace_pci_hp_event(pci_name(ctrl->pcie->port),
+ slot_name(ctrl),
+ PCI_HOTPLUG_LINK_UP);
+ }
ctrl->request_result = pciehp_enable_slot(ctrl);
break;
default:
diff --git a/include/trace/events/pci.h b/include/trace/events/pci.h
new file mode 100644
index 000000000000..208609492c06
--- /dev/null
+++ b/include/trace/events/pci.h
@@ -0,0 +1,63 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM pci
+
+#if !defined(_TRACE_HW_EVENT_PCI_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_HW_EVENT_PCI_H
+
+#include <linux/tracepoint.h>
+
+#define PCI_HOTPLUG_EVENT \
+ EM(PCI_HOTPLUG_LINK_UP, "LINK_UP") \
+ EM(PCI_HOTPLUG_LINK_DOWN, "LINK_DOWN") \
+ EM(PCI_HOTPLUG_CARD_PRESENT, "CARD_PRESENT") \
+ EMe(PCI_HOTPLUG_CARD_NOT_PRESENT, "CARD_NOT_PRESENT")
+
+/* Enums require being exported to userspace, for user tool parsing */
+#undef EM
+#undef EMe
+#define EM(a, b) TRACE_DEFINE_ENUM(a);
+#define EMe(a, b) TRACE_DEFINE_ENUM(a);
+
+PCI_HOTPLUG_EVENT
+
+/*
+ * Now redefine the EM() and EMe() macros to map the enums to the strings
+ * that will be printed in the output.
+ */
+#undef EM
+#undef EMe
+#define EM(a, b) {a, b},
+#define EMe(a, b) {a, b}
+
+TRACE_EVENT(pci_hp_event,
+
+ TP_PROTO(const char *port_name,
+ const char *slot,
+ const int event),
+
+ TP_ARGS(port_name, slot, event),
+
+ TP_STRUCT__entry(
+ __string( port_name, port_name )
+ __string( slot, slot )
+ __field( int, event )
+ ),
+
+ TP_fast_assign(
+ __assign_str(port_name);
+ __assign_str(slot);
+ __entry->event = event;
+ ),
+
+ TP_printk("%s slot:%s, event:%s\n",
+ __get_str(port_name),
+ __get_str(slot),
+ __print_symbolic(__entry->event, PCI_HOTPLUG_EVENT)
+ )
+);
+
+#endif /* _TRACE_HW_EVENT_PCI_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>
diff --git a/include/uapi/linux/pci.h b/include/uapi/linux/pci.h
index a769eefc5139..4f150028965d 100644
--- a/include/uapi/linux/pci.h
+++ b/include/uapi/linux/pci.h
@@ -39,4 +39,11 @@
#define PCIIOC_MMAP_IS_MEM (PCIIOC_BASE | 0x02) /* Set mmap state to MEM space. */
#define PCIIOC_WRITE_COMBINE (PCIIOC_BASE | 0x03) /* Enable/disable write-combining. */

+enum pci_hotplug_event {
+ PCI_HOTPLUG_LINK_UP,
+ PCI_HOTPLUG_LINK_DOWN,
+ PCI_HOTPLUG_CARD_PRESENT,
+ PCI_HOTPLUG_CARD_NOT_PRESENT,
+};
+
#endif /* _UAPILINUX_PCI_H */
--
2.39.3