Re: [PATCH v12 1/3] PCI: trace: Add a generic RAS tracepoint for hotplug event

Steven Rostedt
2025-10-14T15:40:30Z

On Tue, 14 Oct 2025 20:31:57 +0800
Shuai Xue <xueshuai@linux.alibaba.com> wrote:

> 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 following output is generated when a device is hotplugged:
>
> $ echo 1 > /sys/kernel/debug/tracing/events/pci/pci_hp_event/enable
> $ cat /sys/kernel/debug/tracing/trace_pipe
> irq/51-pciehp-88 [001] ..... 1311.177459: pci_hp_event: 0000:00:02.0 slot:10, event:CARD_PRESENT
>
> irq/51-pciehp-88 [001] ..... 1311.177566: pci_hp_event: 0000:00:02.0 slot:10, event:LINK_UP
>
> Suggested-by: Lukas Wunner <lukas@wunner.de>
> Suggested-by: Steven Rostedt <rostedt@goodmis.org>
> Signed-off-by: Shuai Xue <xueshuai@linux.alibaba.com>
> Reviewed-by: Lukas Wunner <lukas@wunner.de>
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> ---
> drivers/pci/Makefile | 3 ++
> drivers/pci/hotplug/pciehp_ctrl.c | 31 ++++++++++++---
> drivers/pci/trace.c | 11 ++++++
> include/trace/events/pci.h | 63 +++++++++++++++++++++++++++++++
> include/uapi/linux/pci.h | 7 ++++
> 5 files changed, 109 insertions(+), 6 deletions(-)
> create mode 100644 drivers/pci/trace.c
> create mode 100644 include/trace/events/pci.h
>
> diff --git a/drivers/pci/Makefile b/drivers/pci/Makefile
> index 67647f1880fb..58a4e4ea76b0 100644
> --- a/drivers/pci/Makefile
> +++ b/drivers/pci/Makefile
> @@ -45,3 +45,6 @@ obj-y += controller/
> obj-y += switch/
>
> subdir-ccflags-$(CONFIG_PCI_DEBUG) := -DDEBUG
> +
> +CFLAGS_trace.o := -I$(src)
> +obj-$(CONFIG_TRACING) += trace.o
> diff --git a/drivers/pci/hotplug/pciehp_ctrl.c b/drivers/pci/hotplug/pciehp_ctrl.c
> index bcc938d4420f..7805f697a02c 100644
> --- a/drivers/pci/hotplug/pciehp_ctrl.c
> +++ b/drivers/pci/hotplug/pciehp_ctrl.c
> @@ -19,6 +19,7 @@
> #include <linux/types.h>
> #include <linux/pm_runtime.h>
> #include <linux/pci.h>
> +#include <trace/events/pci.h>
>
> #include "../pci.h"
> #include "pciehp.h"
> @@ -244,12 +245,20 @@ 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);

I know this is v12 and I don't remember if I suggested this before and you
gave me a reason already, but why not simply pass in "ctrl" and have the
TRACE_EVENT() denote the names?

> + }
> + 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 +278,9 @@ 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 +293,19 @@ 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/drivers/pci/trace.c b/drivers/pci/trace.c
> new file mode 100644
> index 000000000000..cf11abca8602
> --- /dev/null
> +++ b/drivers/pci/trace.c
> @@ -0,0 +1,11 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Tracepoints for PCI system
> + *
> + * Copyright (C) 2025 Alibaba Corporation
> + */
> +
> +#include <linux/pci.h>
> +
> +#define CREATE_TRACE_POINTS
> +#include <trace/events/pci.h>
> 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_PROTO(struct controller *ctrl, int event),

TP_ARGS(ctrl, event),

TP_STRUCT__entry(
__string( port_name, pci_name(ctrl->pcie->port) )
__string( slot, slot_name(ctrl) )
__field( int, event )
),

It would move the work out of the calling path.

-- Steve

> +
> + 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 */