linux-kernel - Re: [PATCH v4] PCI: Relabel JHL6540 on Lenovo X1 Carbon 7,8

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Message-ID: <Zidx4lV2303H88R_@wunner.de>
Date: Tue, 23 Apr 2024 10:31:30 +0200
From: Lukas Wunner <lukas@...ner.de>
To: Mika Westerberg <mika.westerberg@...ux.intel.com>
Cc: Mario Limonciello <mario.limonciello@....com>,
	Esther Shimanovich <eshimanovich@...omium.org>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org, Rajat Jain <rajatja@...gle.com>
Subject: Re: [PATCH v4] PCI: Relabel JHL6540 on Lenovo X1 Carbon 7,8

On Tue, Apr 23, 2024 at 08:33:12AM +0300, Mika Westerberg wrote:
> I think what you are looking for is that anything behind a PCIe tunnel
> should not have this applied. IIRC the AMD GPU or some code there were
> going to add identification of "virtual" links to the bandwidth
> calculation functionality.

I guess I could resurrect my correlation patch:

https://lore.kernel.org/all/f53ea40a7487e145aa1a62c347cef1814072e140.1536517047.git.lukas@wunner.de/

The last time I forward-ported it was for v5.13.  I still have that code
running on my development machine.

The problem is that it only allows lookup from tb_port to pci_dev.
I'd have to add a pointer to struct pci_dev to allow lookups in the
inverse direction.  Though I think we have such PCI companion devices
for CXL as well, so such a pointer could be useful in general.

I'm knee-deep in PCI device authentication code but could probably
dedicate a weekend to the correlation patch if there's interest?

Once we have correlation, we can expose more precise bandwidth
for virtual PCI links in sysfs.

Thanks,

Lukas