linux-kernel - Re: [PATCH v2] KVM: arm64: pmu: Don't increment SW

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Message-ID: <50e04eb9bcd607c6729919d70ae7e82f@kernel.org>
Date:   Mon, 02 Mar 2020 10:50:16 +0000
From:   Marc Zyngier <maz@...nel.org>
To:     Eric Auger <eric.auger@...hat.com>
Cc:     eric.auger.pro@...il.com, stable@...r.kernel.org,
        linux-kernel@...r.kernel.org, kvmarm@...ts.cs.columbia.edu
Subject: Re: [PATCH v2] KVM: arm64: pmu: Don't increment SW_INCR if PMCR.E is
 unset

On 2020-03-02 10:48, Eric Auger wrote:
> commit 3837407c1aa1 upstream.
> 
> The specification says PMSWINC increments PMEVCNTR<n>_EL1 by 1
> if PMEVCNTR<n>_EL0 is enabled and configured to count SW_INCR.
> 
> For PMEVCNTR<n>_EL0 to be enabled, we need both PMCNTENSET to
> be set for the corresponding event counter but we also need
> the PMCR.E bit to be set.
> 
> Fixes: 7a0adc7064b8 ("arm64: KVM: Add access handler for PMSWINC 
> register")
> Signed-off-by: Eric Auger <eric.auger@...hat.com>
> Cc: <stable@...r.kernel.org> # 4.9 and 4.14 only

Reviewed-by: Marc Zyngier <maz@...nel.org>

> 
> ---
> 
> This is a backport of 3837407c1aa1 ("KVM: arm64: pmu: Don't
> increment SW_INCR if PMCR.E is unset") which did not apply on
> 4.9-stable and 4.14-stable trees. Compared to the original patch
> __vcpu_sys_reg() is replaced by vcpu_sys_reg().
> 
> v1 -> v2:
> - this patch also is candidate for 4.9-stable
> ---
>  virt/kvm/arm/pmu.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/virt/kvm/arm/pmu.c b/virt/kvm/arm/pmu.c
> index 69ccce308458..9a47b0cfb01d 100644
> --- a/virt/kvm/arm/pmu.c
> +++ b/virt/kvm/arm/pmu.c
> @@ -299,6 +299,9 @@ void kvm_pmu_software_increment(struct kvm_vcpu
> *vcpu, u64 val)
>  	if (val == 0)
>  		return;
> 
> +	if (!(vcpu_sys_reg(vcpu, PMCR_EL0) & ARMV8_PMU_PMCR_E))
> +		return;
> +
>  	enable = vcpu_sys_reg(vcpu, PMCNTENSET_EL0);
>  	for (i = 0; i < ARMV8_PMU_CYCLE_IDX; i++) {
>  		if (!(val & BIT(i)))

-- 
Jazz is not dead. It just smells funny...