linux-kernel - RE: [PATCH v3 15/29] arm_mpam: Reset MSC controls from cpuhp callbacks

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Message-ID:
 <OSZPR01MB879824B522CCDDE98F30972E8BFAA@OSZPR01MB8798.jpnprd01.prod.outlook.com>
Date: Wed, 29 Oct 2025 06:53:37 +0000
From: "Shaopeng Tan (Fujitsu)" <tan.shaopeng@...itsu.com>
To: 'James Morse' <james.morse@....com>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>, "linux-acpi@...r.kernel.org"
	<linux-acpi@...r.kernel.org>
CC: D Scott Phillips OS <scott@...amperecomputing.com>,
	"carl@...amperecomputing.com" <carl@...amperecomputing.com>,
	"lcherian@...vell.com" <lcherian@...vell.com>, "bobo.shaobowang@...wei.com"
	<bobo.shaobowang@...wei.com>, "baolin.wang@...ux.alibaba.com"
	<baolin.wang@...ux.alibaba.com>, Jamie Iles <quic_jiles@...cinc.com>, Xin Hao
	<xhao@...ux.alibaba.com>, "peternewman@...gle.com" <peternewman@...gle.com>,
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	<amitsinght@...vell.com>, David Hildenbrand <david@...hat.com>, Dave Martin
	<dave.martin@....com>, Koba Ko <kobak@...dia.com>, Shanker Donthineni
	<sdonthineni@...dia.com>, "fenghuay@...dia.com" <fenghuay@...dia.com>,
	"baisheng.gao@...soc.com" <baisheng.gao@...soc.com>, Jonathan Cameron
	<jonathan.cameron@...wei.com>, Rob Herring <robh@...nel.org>, Rohit Mathew
	<rohit.mathew@....com>, Rafael Wysocki <rafael@...nel.org>, Len Brown
	<lenb@...nel.org>, Lorenzo Pieralisi <lpieralisi@...nel.org>, Hanjun Guo
	<guohanjun@...wei.com>, Sudeep Holla <sudeep.holla@....com>, Catalin Marinas
	<catalin.marinas@....com>, Will Deacon <will@...nel.org>, Greg Kroah-Hartman
	<gregkh@...uxfoundation.org>, Danilo Krummrich <dakr@...nel.org>, Jeremy
 Linton <jeremy.linton@....com>, Gavin Shan <gshan@...hat.com>, Rohit Mathew
	<Rohit.Mathew@....com>
Subject: RE: [PATCH v3 15/29] arm_mpam: Reset MSC controls from cpuhp
 callbacks

 
> When a CPU comes online, it may bring a newly accessible MSC with it. Only
> the default partid has its value reset by hardware, and even then the MSC might
> not have been reset since its config was previously dirtied. e.g. Kexec.
> 
> Any in-use partid must have its configuration restored, or reset.
> In-use partids may be held in caches and evicted later.
> 
> MSC are also reset when CPUs are taken offline to cover cases where firmware
> doesn't reset the MSC over reboot using UEFI, or kexec where there is no
> firmware involvement.
> 
> If the configuration for a RIS has not been touched since it was brought online,
> it does not need resetting again.
> 
> To reset, write the maximum values for all discovered controls.
> 
> CC: Rohit Mathew <Rohit.Mathew@....com>
> Signed-off-by: James Morse <james.morse@....com>
> Reviewed-by: Fenghua Yu <fenghuay@...dia.com>
> Tested-by: Fenghua Yu <fenghuay@...dia.com>


Reviewed-by: Shaopeng Tan <tan.shaopeng@...fujitsu.com>