[PATCH 2/2] KVM: arm/arm64: Fix timer enable flow

[Marc Zyngier]

On Fri, 15 Dec 2017 14:16:56 +0000,
Christoffer Dall wrote:
> 
> When enabling the timer on the first run, we fail to ever restore the
> state and mark it as loaded.  That means, that in the initial entry to
> the VCPU ioctl, unless we exit to userspace for some reason such as a
> pending signal, if the guest programs a timer and blocks, we will wait
> forever, because we never read back the hardware state (the loaded flag
> is not set), and so we think the timer is disabled, and we never
> schedule a background soft timer.
> 
> The end result?  The VCPU blocks forever, and the only solution is to
> kill the thread.
> 
> Fixes: 4a2c4da1250d ("arm/arm64: KVM: Load the timer state when enabling the timer")
> Reported-by: Marc Zyngier <marc.zyngier at arm.com>
> Signed-off-by: Christoffer Dall <christoffer.dall at linaro.org>
> ---
>  virt/kvm/arm/arch_timer.c | 5 +----
>  1 file changed, 1 insertion(+), 4 deletions(-)
> 
> diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c
> index 14c018f990a7..cc29a8148328 100644
> --- a/virt/kvm/arm/arch_timer.c
> +++ b/virt/kvm/arm/arch_timer.c
> @@ -846,10 +846,7 @@ int kvm_timer_enable(struct kvm_vcpu *vcpu)
>  no_vgic:
>  	preempt_disable();
>  	timer->enabled = 1;
> -	if (!irqchip_in_kernel(vcpu->kvm))
> -		kvm_timer_vcpu_load_user(vcpu);
> -	else
> -		kvm_timer_vcpu_load_vgic(vcpu);
> +	kvm_timer_vcpu_load(vcpu);
>  	preempt_enable();
>  
>  	return 0;
> -- 
> 2.14.2
> 

Reviewed-by: Marc Zyngier <marc.zyngier at arm.com>
Tested-by: Marc Zyngier <marc.zyngier at arm.com>

	M.