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

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Message-ID: <11119800-3b6a-a683-3500-115a057c2826@linux.intel.com>
Date: Mon, 21 Jul 2025 13:18:32 +0300 (EEST)
From: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To: Shuai Xue <xueshuai@...ux.alibaba.com>
cc: Matthew W Carlis <mattc@...estorage.com>, helgaas@...nel.org, 
    Lukas Wunner <lukas@...ner.de>, anil.s.keshavamurthy@...el.com, 
    bhelgaas@...gle.com, bp@...en8.de, davem@...emloft.net, 
    linux-edac@...r.kernel.org, LKML <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, 18 Jul 2025, 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.
> 
> 
> 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.

Ah, I only now noticed you've decided to re-place them. Please disregard 
my other comment about this being still open/undecided item.

> 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?

Since you're probably quite far with the pcie link event patch too given 
above, could you take a look at the LNKSTA flags representation in my 
patch and incorporate those as well as there seems to always lot of 
uncertainty about those flags when investigating the LBMS/bwctrl related 
issues so it seems prudent to explicitly include them into the traceevent 
output:

https://lore.kernel.org/linux-pci/7c289bba-3133-0989-6333-41fc41fe3504@linux.intel.com/


-- 
 i.