linux-kernel - Re: [PATCH v3 1/1] PCI: Add Extended Tag + MRRS quirk for Xeon 6

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <aFQHBL0oWo6GTSQG@wunner.de>
Date: Thu, 19 Jun 2025 14:48:04 +0200
From: Lukas Wunner <lukas@...ner.de>
To: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Cc: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
	Dan Williams <dan.j.williams@...el.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
	"H. Peter Anvin" <hpa@...or.com>, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/1] PCI: Add Extended Tag + MRRS quirk for Xeon 6

On Tue, Jun 10, 2025 at 02:48:02PM +0300, Ilpo Järvinen wrote:
> When bifurcated to x2, Xeon 6 Root Port performance is sensitive to the
> configuration of Extended Tags, Max Read Request Size (MRRS), and 10-Bit
> Tag Requester (note: there is currently no 10-Bit Tag support in the
> kernel). While those can be configured to the recommended values by FW,
> kernel may decide to overwrite the initial values.
> 
> Add a quirk that disallows enabling Extended Tags and setting MRRS
> larger than 128B for devices under Xeon 6 Root Ports if the Root Port
> is bifurcated to x2. Use the host bridge's enable_device hook to
> overwrite MRRS if it's set to >128B for the device to be enabled.
> 
> The earlier attempts to implement this quirk polluted PCI core code
> with the checks necessary to support this quirk. Using the
> enable_device hook keeps the quirk well-contained, away from the PCI
> core code.
> 
> Suggested-by: Lukas Wunner <lukas@...ner.de>
> Link: https://cdrdv2.intel.com/v1/dl/getContent/837176
> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>

Reviewed-by: Lukas Wunner <lukas@...ner.de>

Patch looks perfect to me and could go in either through pci or tip.


For the record, link to previous attempt to solve this:

https://lore.kernel.org/r/20250422130207.3124-1-ilpo.jarvinen@linux.intel.com/

Thanks,

Lukas