Re: [PATCH v1 0/2] PCI: Add pci=nobwctrl to disable the PCIe bandwidth controller

[Lukas Wunner <lukas@wunner.de>]

On Wed, Jul 29, 2026 at 11:45:03AM +0800, Guixin Liu wrote:
> Enabling the PCIe bandwidth controller sets the Link Bandwidth Management
> Interrupt Enable (LBMIE) and Link Autonomous Bandwidth Interrupt Enable
> (LABIE) bits.  On some (typically old) platforms this has been observed to
> cause boot hangs; commit 46a9f70e93ef ("PCI/bwctrl: Disable BW controller
> on Intel P45 using a quirk") works around one such platform with a
> per-device quirk.
> 
> A per-device quirk only helps once the offending device is identified and
> a quirk has shipped, which is awkward for a boot hang since the machine
> cannot be booted to report the culprit.  The only existing escape hatch,
> pcie_ports=compat, is a blunt instrument that also disables AER, PME,
> hotplug and DPC.

Ideally we want to identify all devices that have problems if the
bandwidth controller is enabled and add quirks for every one of them.

In a sense, a command line option disincentivizes reporting and
fixing affected devices because users can just work around the problem.

Additionally, there is a general dislike in the community for
adding new command line options.

Are you seeing issues on different devices than the one that's
already been quirked?  If so, a patch to add quirks for them
would be welcome.

Thanks,

Lukas