linux-kernel - Re: [PATCH v4 09/41] arm64: mpam: Initialise and context switch the MPAMSM

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Message-ID: <aYTLcdkmmzMMykYM@arm.com>
Date: Thu, 5 Feb 2026 16:55:13 +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,
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	Shaopeng Tan <tan.shaopeng@...fujitsu.com>
Subject: Re: [PATCH v4 09/41] arm64: mpam: Initialise and context switch the
 MPAMSM_EL1 register

On Tue, Feb 03, 2026 at 09:43:10PM +0000, Ben Horgan wrote:
> The MPAMSM_EL1 sets the MPAM labels, PMG and PARTID, for loads and stores
> generated by a shared SMCU. Disable the traps so the kernel can use it and
> set it to the same configuration as the per-EL cpu MPAM configuration.
> 
> If an SMCU is not shared with other cpus then it is implementation
> defined whether the configuration from MPAMSM_EL1 is used or that from
> the appropriate MPAMy_ELx. As we set the same, PMG_D and PARTID_D,
> configuration for MPAM0_EL1, MPAM1_EL1 and MPAMSM_EL1 the resulting
> configuration is the same regardless.
> 
> The range of valid configurations for the PARTID and PMG in MPAMSM_EL1 is
> not currently specified in Arm Architectural Reference Manual but the
> architect has confirmed that it is intended to be the same as that for the
> cpu configuration in the MPAMy_ELx registers.
> 
> Tested-by: Gavin Shan <gshan@...hat.com>
> Tested-by: Shaopeng Tan <tan.shaopeng@...fujitsu.com>
> Tested-by: Peter Newman <peternewman@...gle.com>
> Reviewed-by: Jonathan Cameron <jonathan.cameron@...wei.com>
> Reviewed-by: Gavin Shan <gshan@...hat.com>
> Signed-off-by: Ben Horgan <ben.horgan@....com>

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