linux-kernel - Re: [RFC PATCH 13/36] arm_mpam: Add probe/remove for mpam msc driver and kbuild boiler plate

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: <aIIiazUK4S_G6loe@arm.com>
Date: Thu, 24 Jul 2025 13:09:15 +0100
From: Catalin Marinas <catalin.marinas@....com>
To: James Morse <james.morse@....com>
Cc: linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	Rob Herring <robh@...nel.org>, Ben Horgan <ben.horgan@....com>,
	Rohit Mathew <rohit.mathew@....com>,
	Shanker Donthineni <sdonthineni@...dia.com>,
	Zeng Heng <zengheng4@...wei.com>,
	Lecopzer Chen <lecopzerc@...dia.com>,
	Carl Worth <carl@...amperecomputing.com>,
	shameerali.kolothum.thodi@...wei.com,
	D Scott Phillips OS <scott@...amperecomputing.com>,
	lcherian@...vell.com, bobo.shaobowang@...wei.com,
	tan.shaopeng@...itsu.com, baolin.wang@...ux.alibaba.com,
	Jamie Iles <quic_jiles@...cinc.com>,
	Xin Hao <xhao@...ux.alibaba.com>, peternewman@...gle.com,
	dfustini@...libre.com, amitsinght@...vell.com,
	David Hildenbrand <david@...hat.com>,
	Rex Nie <rex.nie@...uarmicro.com>,
	Dave Martin <dave.martin@....com>, Koba Ko <kobak@...dia.com>
Subject: Re: [RFC PATCH 13/36] arm_mpam: Add probe/remove for mpam msc driver
 and kbuild boiler plate

On Fri, Jul 11, 2025 at 06:36:25PM +0000, James Morse wrote:
> Probing MPAM is convoluted. MSCs that are integrated with a CPU may
> only be accessible from those CPUs, and they may not be online.
> Touching the hardware early is pointless as MPAM can't be used until
> the system-wide common values for num_partid and num_pmg have been
> discovered.
> 
> Start with driver probe/remove and mapping the MSC.
> 
> CC: Carl Worth <carl@...amperecomputing.com>
> Signed-off-by: James Morse <james.morse@....com>
> ---
>  arch/arm64/Kconfig                          |   1 +
>  drivers/platform/arm64/Kconfig              |   1 +
>  drivers/platform/arm64/Makefile             |   1 +
>  drivers/platform/arm64/mpam/Kconfig         |  10 +
>  drivers/platform/arm64/mpam/Makefile        |   4 +
>  drivers/platform/arm64/mpam/mpam_devices.c  | 336 ++++++++++++++++++++
>  drivers/platform/arm64/mpam/mpam_internal.h |  62 ++++
>  7 files changed, 415 insertions(+)
>  create mode 100644 drivers/platform/arm64/mpam/Kconfig
>  create mode 100644 drivers/platform/arm64/mpam/Makefile
>  create mode 100644 drivers/platform/arm64/mpam/mpam_devices.c
>  create mode 100644 drivers/platform/arm64/mpam/mpam_internal.h

Bikeshedding: why not drivers/resctrl to match fs/resctrl? We wouldn't
need the previous patch either to move the arm64 platform drivers.

I'm not an expert on resctrl but the MPAM code looks more like a backend
for the resctrl support, so it makes more sense to do as we did for
other drivers like irqchip, iommu. You can create drivers/resctrl/arm64
if you want to keep them grouped.

-- 
Catalin