linux-kernel - Re: [PATCH v3 09/47] arm64: mpam: Add cpu

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: <aWkv0jsX-tMHEo9G@arm.com>
Date: Thu, 15 Jan 2026 18:20:02 +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
Subject: Re: [PATCH v3 09/47] arm64: mpam: Add cpu_pm notifier to restore
 MPAM sysregs

On Mon, Jan 12, 2026 at 04:58:36PM +0000, Ben Horgan wrote:
> +static int mpam_pm_notifier(struct notifier_block *self,
> +			    unsigned long cmd, void *v)
> +{
> +	u64 regval;
> +	int cpu = smp_processor_id();
> +
> +	switch (cmd) {
> +	case CPU_PM_EXIT:
> +		/*
> +		 * Don't use mpam_thread_switch() as the system register
> +		 * value has changed under our feet.
> +		 */
> +		regval = READ_ONCE(per_cpu(arm64_mpam_current, cpu));
> +		write_sysreg_s(regval, SYS_MPAM1_EL1);
> +		isb();
> +
> +		write_sysreg_s(regval, SYS_MPAM0_EL1);
> +
> +		return NOTIFY_OK;
> +	default:
> +		return NOTIFY_DONE;
> +	}
> +}

This looks fine unless we decide to save/restore them in the low-level
suspend/resume functions.

-- 
Catalin