linux-kernel - Re: [PATCH v3 02/14] arm64: Allow mismatched 32-bit EL0 support

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Message-ID: <jhjblftwpqq.mognet@arm.com>
Date:   Thu, 19 Nov 2020 11:27:41 +0000
From:   Valentin Schneider <valentin.schneider@....com>
To:     Will Deacon <will@...nel.org>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-arch@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Catalin Marinas <catalin.marinas@....com>,
        Marc Zyngier <maz@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Morten Rasmussen <morten.rasmussen@....com>,
        Qais Yousef <qais.yousef@....com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Quentin Perret <qperret@...gle.com>, Tejun Heo <tj@...nel.org>,
        Li Zefan <lizefan@...wei.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Ingo Molnar <mingo@...hat.com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        kernel-team@...roid.com
Subject: Re: [PATCH v3 02/14] arm64: Allow mismatched 32-bit EL0 support


On 13/11/20 09:37, Will Deacon wrote:
> +const struct cpumask *system_32bit_el0_cpumask(void)
> +{
> +	if (!system_supports_32bit_el0())
> +		return cpu_none_mask;
> +
> +	if (static_branch_unlikely(&arm64_mismatched_32bit_el0))
> +		return cpu_32bit_el0_mask;
> +
> +	return cpu_present_mask;
> +}

Nit: this is used in patch 13 to implement arch_cpu_allowed_mask(). Since
that latter defaults to cpu_possible_mask, this probably should too.