linux-kernel - Re: [PATCH v8 04/13] KVM: arm64: PMU: Set PMCR_EL0.N for vCPU based on the associated PMU

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Message-ID: <ZTeM2RnMCRFoGsZd@linux.dev>
Date:   Tue, 24 Oct 2023 09:22:33 +0000
From:   Oliver Upton <oliver.upton@...ux.dev>
To:     Raghavendra Rao Ananta <rananta@...gle.com>
Cc:     Marc Zyngier <maz@...nel.org>,
        Alexandru Elisei <alexandru.elisei@....com>,
        James Morse <james.morse@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Zenghui Yu <yuzenghui@...wei.com>,
        Shaoqin Huang <shahuang@...hat.com>,
        Jing Zhang <jingzhangos@...gle.com>,
        Reiji Watanabe <reijiw@...gle.com>,
        Colton Lewis <coltonlewis@...gle.com>,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH v8 04/13] KVM: arm64: PMU: Set PMCR_EL0.N for vCPU based
 on the associated PMU

On Fri, Oct 20, 2023 at 09:40:44PM +0000, Raghavendra Rao Ananta wrote:

[...]

> +int kvm_arm_pmu_get_max_counters(struct kvm *kvm)
> +{
> +	struct arm_pmu *arm_pmu = kvm->arch.arm_pmu;
> +
> +	lockdep_assert_held(&kvm->arch.config_lock);

This lockdep assertion is misleading. Readers of kvm_arch::arm_pmu *are
not* serialized by the config_lock.

-- 
Thanks,
Oliver