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

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Message-ID: <15e8e19d-d471-69da-b928-afc20ee9a584@linux.intel.com>
Date: Tue, 20 May 2025 13:59:17 +0300 (EEST)
From: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To: Lukas Wunner <lukas@...ner.de>, Shuai Xue <xueshuai@...ux.alibaba.com>
cc: rostedt@...dmis.org, linux-pci@...r.kernel.org, 
    LKML <linux-kernel@...r.kernel.org>, linux-edac@...r.kernel.org, 
    linux-trace-kernel@...r.kernel.org, helgaas@...nel.org, 
    bhelgaas@...gle.com, tony.luck@...el.com, bp@...en8.de, 
    mhiramat@...nel.org, mathieu.desnoyers@...icios.com, oleg@...hat.com, 
    naveen@...nel.org, davem@...emloft.net, anil.s.keshavamurthy@...el.com, 
    mark.rutland@....com, peterz@...radead.org, tianruidong@...ux.alibaba.com
Subject: Re: [PATCH v8] PCI: hotplug: Add a generic RAS tracepoint for hotplug
 event

On Tue, 20 May 2025, Lukas Wunner wrote:

> On Tue, May 20, 2025 at 01:07:28PM +0300, Ilpo Järvinen wrote:
> > On Tue, 20 May 2025, Shuai Xue wrote:
> > > , and the format of "Link Speed changed" is a bit different from 
> > > "pci_hp_event".
> > 
> > The difference is only because when the Link is down, there's no Link
> > Speed (obviously). Whenever a new device is hotplugged and it comes up, 
> > there's also Link Speed for it which can be included into the trace event. 
> > 
> > I think the trace event should have some special value for the fields that 
> > are N/A due to Link being off. While it would be possible to create 
> > separate events for speed changes and hotplug, I don't see any pros in 
> > that approach over just having the N/A fields marked as such when the Link 
> > is Down.
> 
> Link speed changes and device plug/unplug events are orthogonal,
> I don't think they should be mixed together in the same event.
> 
> A link speed event can be signaled simultaneously to a plug event
> and then user space can decide in which type of event it's
> interested in.
> 
> That also avoids the awkwardness of having N/A values for the
> link speed on unplug.

Fair enough.

-- 
 i.