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Date: Thu, 7 Dec 2023 13:51:36 +0000
From: Catalin Marinas <catalin.marinas@arm.com>
To: Joey Gouly <joey.gouly@arm.com>
Cc: linux-arm-kernel@lists.infradead.org, akpm@linux-foundation.org,
	aneesh.kumar@linux.ibm.com, broonie@kernel.org,
	dave.hansen@linux.intel.com, maz@kernel.org, oliver.upton@linux.dev,
	shuah@kernel.org, will@kernel.org, kvmarm@lists.linux.dev,
	linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
	linux-kselftest@vger.kernel.org, James Morse <james.morse@arm.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Zenghui Yu <yuzenghui@huawei.com>
Subject: Re: [PATCH v3 05/25] arm64: context switch POR_EL0 register
Message-ID: <ZXHN6IFeZLz-mFau@arm.com>
References: <20231124163510.1835740-1-joey.gouly@arm.com>
 <20231124163510.1835740-6-joey.gouly@arm.com>
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In-Reply-To: <20231124163510.1835740-6-joey.gouly@arm.com>

On Fri, Nov 24, 2023 at 04:34:50PM +0000, Joey Gouly wrote:
> @@ -498,6 +508,17 @@ static void erratum_1418040_new_exec(void)
>  	preempt_enable();
>  }
>  
> +static void permission_overlay_switch(struct task_struct *next)
> +{
> +	if (system_supports_poe()) {
> +		current->thread.por_el0 = read_sysreg_s(SYS_POR_EL0);
> +		if (current->thread.por_el0 != next->thread.por_el0) {
> +			write_sysreg_s(next->thread.por_el0, SYS_POR_EL0);
> +			isb();
> +		}
> +	}

Nitpick: use "if (!system_supports_poe()) return;" to avoid too much
indentation.

W.r.t. the isb(), I think we accumulated quite a lot on this path. It
might be worth going through them and having one at the end, where
possible.

-- 
Catalin