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

[Shuai Xue <xueshuai@linux.alibaba.com>]

在 2025/10/14 23:40, Steven Rostedt 写道:
> 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, 


Aha, in our previous email discussions regarding the tracepoint
implementation, you provided many constructive suggestions, so I added
the Suggested-by tag. Perhaps I misunderstood the meaning of
Suggested-by - I will drop it.


> but why not simply pass in "ctrl" and have the
> TRACE_EVENT() denote the names?

Sure, I will send a version.

>> +		}
>> +		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.
> 

I see.

> -- Steve


Thanks.

Best Regards,
Shuai