linux-kernel - Re: [PATCH v8] PCI: hotplug: Add a generic RAS tracepoint for hotplug event

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Message-ID: <e92f8d1f-457c-4248-8397-81b0e20ff4af@linux.alibaba.com>
Date: Fri, 18 Jul 2025 13:29:18 +0800
From: Shuai Xue <xueshuai@...ux.alibaba.com>
To: Matthew W Carlis <mattc@...estorage.com>, helgaas@...nel.org,
 lukas@...ner.de, Ilpo Järvinen
 <ilpo.jarvinen@...ux.intel.com>
Cc: anil.s.keshavamurthy@...el.com, bhelgaas@...gle.com, bp@...en8.de,
 davem@...emloft.net, ilpo.jarvinen@...ux.intel.com,
 linux-edac@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-pci@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
 lukas@...ner.de, mark.rutland@....com, mathieu.desnoyers@...icios.com,
 mhiramat@...nel.org, naveen@...nel.org, oleg@...hat.com,
 peterz@...radead.org, rostedt@...dmis.org, tianruidong@...ux.alibaba.com,
 tony.luck@...el.com
Subject: Re: [PATCH v8] PCI: hotplug: Add a generic RAS tracepoint for hotplug
 event



在 2025/7/18 11:46, Matthew W Carlis 写道:
> On Thu, Jul 17, 2025 Bjorn Helgaas wrote
>> So I think your idea of adding current link speed/width to the "Link
>> Up" event is still on the table, and that does sound useful to me.
> 
> We're already reading the link status register here to check DLLA so
> it would be nice. I guess if everything is healthy we're probably already
> at the maximum speed by this point.
> 
>> In the future we might add another tracepoint when we enumerate the
>> device and know the Vendor/Device ID.
> 
> I think we might have someone who would be interested in doing it.


Hi, all,

IIUC, the current hotplug event (or presence event) is enough for Matthew.
and we would like a new tracepoing for link speed change which reports
speeds.

For hotplug event, I plan to send a new version to

1. address Bjorn' concerns about event strings by removing its spaces.

#define PCI_HOTPLUG_EVENT							\
	EM(PCI_HOTPLUG_LINK_UP,			"PCI_HOTPLUG_LINK_UP")		\
	EM(PCI_HOTPLUG_LINK_DOWN,		"PCI_HOTPLUG_LINK_DOWN")	\
	EM(PCI_HOTPLUG_CARD_PRESENT,		"PCI_HOTPLUG_CARD_PRESENT")	\
	EMe(PCI_HOTPLUG_CARD_NOT_PRESENT,	"PCI_HOTPLUG_CARD_NOT_PRESENT")

2. address Ilpo comments by moving pci_hp_event to a common place
(include/trace/events/pci.h) so that the new comming can also use it.

For link speed change event (perhaps named as pci_link_event),
I plan to send a seperate patch, which provides:

	TP_STRUCT__entry(
		__string(	port_name,	port_name	)
		__field(	unsigned char,	cur_bus_speed	)
		__field(	unsigned char,	max_bus_speed	)
  		__field(	unsigned char,	width		)
  		__field(	unsigned int,	flit_mode	)
		__field(	unsigned char,	reason		)
		),

The reason field is from Lukas ideas which indicates why the link speed
changed, e.g. "hotplug", "autonomous", "thermal", "retrain", etc.

Are you happy with above changes?

Thanks.
Shuai