linux-kernel - Re: [PATCH v4 10/41] arm64: mpam: Add helpers to change a task or cpu's MPAM PARTID/PMG values

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Message-ID: <aYTLumWRtV9wnO-D@arm.com>
Date: Thu, 5 Feb 2026 16:56:26 +0000
From: Catalin Marinas <catalin.marinas@....com>
To: Ben Horgan <ben.horgan@....com>
Cc: amitsinght@...vell.com, baisheng.gao@...soc.com,
	baolin.wang@...ux.alibaba.com, carl@...amperecomputing.com,
	dave.martin@....com, david@...nel.org, dfustini@...libre.com,
	fenghuay@...dia.com, gshan@...hat.com, james.morse@....com,
	jonathan.cameron@...wei.com, kobak@...dia.com, lcherian@...vell.com,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	peternewman@...gle.com, punit.agrawal@....qualcomm.com,
	quic_jiles@...cinc.com, reinette.chatre@...el.com,
	rohit.mathew@....com, scott@...amperecomputing.com,
	sdonthineni@...dia.com, tan.shaopeng@...itsu.com,
	xhao@...ux.alibaba.com, will@...nel.org, corbet@....net,
	maz@...nel.org, oupton@...nel.org, joey.gouly@....com,
	suzuki.poulose@....com, kvmarm@...ts.linux.dev,
	zengheng4@...wei.com, linux-doc@...r.kernel.org,
	Shaopeng Tan <tan.shaopeng@...fujitsu.com>
Subject: Re: [PATCH v4 10/41] arm64: mpam: Add helpers to change a task or
 cpu's MPAM PARTID/PMG values

On Tue, Feb 03, 2026 at 09:43:11PM +0000, Ben Horgan wrote:
> From: James Morse <james.morse@....com>
> 
> Care must be taken when modifying the PARTID and PMG of a task in any
> per-task structure as writing these values may race with the task being
> scheduled in, and reading the modified values.
> 
> Add helpers to set the task properties, and the CPU default value.  These
> use WRITE_ONCE() that pairs with the READ_ONCE() in mpam_get_regval() to
> avoid causing torn values.
> 
> Tested-by: Gavin Shan <gshan@...hat.com>
> Tested-by: Shaopeng Tan <tan.shaopeng@...fujitsu.com>
> Tested-by: Peter Newman <peternewman@...gle.com>
> CC: Dave Martin <Dave.Martin@....com>
> Reviewed-by: Jonathan Cameron <jonathan.cameron@...wei.com>
> Signed-off-by: James Morse <james.morse@....com>
> Signed-off-by: Ben Horgan <ben.horgan@....com>

Reviewed-by: Catalin Marinas <catalin.marinas@....com>