linux-kernel - Re: [PATCH v9 6/9] PCI/bwctrl: Re-add BW notification portdrv as PCIe BW controller

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Message-ID: <Z3cFfhHirAgxjmDQ@wunner.de>
Date: Thu, 2 Jan 2025 22:30:38 +0100
From: Lukas Wunner <lukas@...ner.de>
To: Niklas Schnelle <niks@...nel.org>
Cc: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
	linux-pci@...r.kernel.org, Bjorn Helgaas <bhelgaas@...gle.com>,
	Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
	Rob Herring <robh@...nel.org>, Krzysztof Wilczy??ski <kw@...ux.com>,
	"Maciej W . Rozycki" <macro@...am.me.uk>,
	Jonathan Cameron <Jonathan.Cameron@...wei.com>,
	Alexandru Gagniuc <mr.nuke.me@...il.com>,
	Krishna chaitanya chundru <quic_krichai@...cinc.com>,
	Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
	"Rafael J . Wysocki" <rafael@...nel.org>, linux-pm@...r.kernel.org,
	Smita Koralahalli <Smita.KoralahalliChannabasappa@....com>,
	linux-kernel@...r.kernel.org,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Amit Kucheria <amitk@...nel.org>, Zhang Rui <rui.zhang@...el.com>,
	Christophe JAILLET <christophe.jaillet@...adoo.fr>,
	Evert Vorster <evorster@...il.com>
Subject: Re: [PATCH v9 6/9] PCI/bwctrl: Re-add BW notification portdrv as
 PCIe BW controller

[cc += Evert]

On Fri, Dec 06, 2024 at 07:12:37PM +0100, Niklas Schnelle wrote:
> On Fri, 2024-10-18 at 17:47 +0300, Ilpo Järvinen wrote:
> > This mostly reverts the commit b4c7d2076b4e ("PCI/LINK: Remove
> > bandwidth notification"). An upcoming commit extends this driver
> > building PCIe bandwidth controller on top of it.
> > 
> > The PCIe bandwidth notification were first added in the commit
> > e8303bb7a75c ("PCI/LINK: Report degraded links via link bandwidth
> > notification") but later had to be removed. The significant changes
> > compared with the old bandwidth notification driver include:
[...]
> I bisected a v6.13-rc1 boot hang on my personal workstation to this
> patch. Sadly I don't have much details like a panic or so because the
> boot hangs before any kernel messages, or at least they're not visible
> long enough to see. I haven't yet looked into the code as I wanted to
> raise awareness first. Since the commit doesn't revert cleanly on
> v6.13-rc1 I also haven't tried that yet.

Hi Niklas,

another regression caused by bandwidth control was reported,
this time it's a hang on shutdown (instead of on boot) and
this time we root-caused it instead of just working around it.

Here's the proposed fix:
https://lore.kernel.org/r/0ee5faf5395cad8d29fb66e1ec444c8d882a4201.1735852688.git.lukas@wunner.de/

Could you test this on top of v6.13-rc1 (or any other rc which
does not include 774c71c52aa4 ("PCI/bwctrl: Enable only if more
than one speed is supported")?

I suspect that it may fix the issue you were seeing as well and
I'm curious whether that suspicion is correct.

Thanks!

Lukas