linux-kernel - Re: [PATCH] KVM: arm64: Use the correct timer for accessing CNT

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Message-ID: <7ed91b9b-e968-770c-28f9-0ca479359657@huawei.com>
Date:   Mon, 16 Mar 2020 18:49:51 +0800
From:   Zenghui Yu <yuzenghui@...wei.com>
To:     KarimAllah Ahmed <karahmed@...zon.de>,
        <linux-kernel@...r.kernel.org>
CC:     Marc Zyngier <maz@...nel.org>, <kvmarm@...ts.cs.columbia.edu>,
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] KVM: arm64: Use the correct timer for accessing CNT

Hi,

On 2020/3/16 17:39, KarimAllah Ahmed wrote:
> Use the physical timer object when reading the physical timer counter
> instead of using the virtual timer object. This is only visible when
> reading it from user-space as kvm_arm_timer_get_reg() is only executed on
> the get register patch from user-space.

s/patch/path/

I think the physical counter hasn't yet been accessed by the current
userspace, wrong?

> 
> Cc: Marc Zyngier <maz@...nel.org>
> Cc: James Morse <james.morse@....com>
> Cc: Julien Thierry <julien.thierry.kdev@...il.com>
> Cc: Suzuki K Poulose <suzuki.poulose@....com>
> Cc: linux-arm-kernel@...ts.infradead.org
> Cc: kvmarm@...ts.cs.columbia.edu
> Cc: linux-kernel@...r.kernel.org
> Signed-off-by: KarimAllah Ahmed <karahmed@...zon.de>

Reviewed-by: Zenghui Yu <yuzenghui@...wei.com>

And this might also deserve:

Fixes: 84135d3d18da ("KVM: arm/arm64: consolidate arch timer trap handlers")


Thanks.

> ---
>   virt/kvm/arm/arch_timer.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c
> index 0d9438e..93bd59b 100644
> --- a/virt/kvm/arm/arch_timer.c
> +++ b/virt/kvm/arm/arch_timer.c
> @@ -788,7 +788,7 @@ u64 kvm_arm_timer_get_reg(struct kvm_vcpu *vcpu, u64 regid)
>   					  vcpu_ptimer(vcpu), TIMER_REG_CTL);
>   	case KVM_REG_ARM_PTIMER_CNT:
>   		return kvm_arm_timer_read(vcpu,
> -					  vcpu_vtimer(vcpu), TIMER_REG_CNT);
> +					  vcpu_ptimer(vcpu), TIMER_REG_CNT);
>   	case KVM_REG_ARM_PTIMER_CVAL:
>   		return kvm_arm_timer_read(vcpu,
>   					  vcpu_ptimer(vcpu), TIMER_REG_CVAL);
>