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

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Message-ID: <20250718163532.GA2700834@bhelgaas>
Date: Fri, 18 Jul 2025 11:35:32 -0500
From: Bjorn Helgaas <helgaas@...nel.org>
To: Shuai Xue <xueshuai@...ux.alibaba.com>
Cc: Matthew W Carlis <mattc@...estorage.com>, lukas@...ner.de,
	Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
	anil.s.keshavamurthy@...el.com, bhelgaas@...gle.com, bp@...en8.de,
	davem@...emloft.net, linux-edac@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
	linux-trace-kernel@...r.kernel.org, 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

On Fri, Jul 18, 2025 at 01:29:18PM +0800, Shuai Xue wrote:
> 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.
> 
> 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?

Seems good to me.

What do you plan for PCI_HOTPLUG_LINK_UP?  It would be nice to have
the link info there since that's sort of a link speed change itself.

Bjorn