linux-kernel - Re: [PATCH v2 3/4] KVM: arm/arm64: check power

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Date:	Mon, 31 Aug 2015 12:12:24 +0200
From:	Christoffer Dall <christoffer.dall@...aro.org>
To:	Eric Auger <eric.auger@...aro.org>
Cc:	eric.auger@...com, marc.zyngier@....com, drjones@...hat.com,
	linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
	kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
	patches@...aro.org, pbonzini@...hat.com
Subject: Re: [PATCH v2 3/4] KVM: arm/arm64: check power_off in critical
 section before VCPU run

On Fri, Aug 07, 2015 at 06:08:32PM +0200, Eric Auger wrote:
> In case KVM_SET_MP_STATE ioctl is called just after we executed the
> vcpu_sleep check, we can enter the guest although KVM_MP_STATE_STOPPED
> is set. Let's check the power_off state in the critical section,
> just before entering the guest.

I don't think this can happen from the KVM_SET_MP_STATE, because that is
a vcpu ioctl and would therefore require userspace sets this before even
entering the run loop in the kernel, but it could happen at the PSCI
system event preparation.

> 
> Signed-off-by: Eric Auger <eric.auger@...aro.org>
> Reported-by: Christoffer Dall <christoffer.dall@...aro.org>
> ---
>  arch/arm/kvm/arm.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
> index 4f50be3..cc404a8 100644
> --- a/arch/arm/kvm/arm.c
> +++ b/arch/arm/kvm/arm.c
> @@ -555,7 +555,8 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
>  			run->exit_reason = KVM_EXIT_INTR;
>  		}
>  
> -		if (ret <= 0 || need_new_vmid_gen(vcpu->kvm)) {
> +		if (ret <= 0 || need_new_vmid_gen(vcpu->kvm) ||
> +			vcpu->arch.power_off) {
>  			local_irq_enable();
>  			kvm_vgic_sync_hwstate(vcpu);
>  			preempt_enable();
> -- 
> 1.9.1
> 
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