Re: [PATCH 01/10] arm/arm64: KVM: Fix ordering of timer/GIC on guest entry

["Alex Bennée" <alex.bennee@linaro.org>]

Marc Zyngier <marc.zyngier@arm.com> writes:

> As we now inject the timer interrupt when we're about to enter
> the guest, it makes a lot more sense to make sure this happens
> before the vgic code queues the pending interrupts.
>
> Otherwise, we get the interrupt on the following exit, which is
> not great for latency (and leads to all kind of bizarre issues
> when using with active interrupts at the HW level).
>
> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
> ---
>  arch/arm/kvm/arm.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
> index d9631ec..46db690 100644
> --- a/arch/arm/kvm/arm.c
> +++ b/arch/arm/kvm/arm.c
> @@ -529,9 +529,10 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
>  		if (vcpu->arch.pause)
>  			vcpu_pause(vcpu);
>  
> -		kvm_vgic_flush_hwstate(vcpu);
>  		kvm_timer_flush_hwstate(vcpu);
>  
> +		kvm_vgic_flush_hwstate(vcpu);
> +
>  		local_irq_disable();
>  
>  		/*
> @@ -544,8 +545,8 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
>  
>  		if (ret <= 0 || need_new_vmid_gen(vcpu->kvm)) {
>  			local_irq_enable();
> -			kvm_timer_sync_hwstate(vcpu);
>  			kvm_vgic_sync_hwstate(vcpu);
> +			kvm_timer_sync_hwstate(vcpu);
>  			continue;
>  		}
>  
> @@ -577,9 +578,10 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
>  		 * Back from guest
>  		 *************************************************************/
>  
> -		kvm_timer_sync_hwstate(vcpu);
>  		kvm_vgic_sync_hwstate(vcpu);
>  
> +		kvm_timer_sync_hwstate(vcpu);
> +
>  		ret = handle_exit(vcpu, run, ret);
>  	}

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>

-- 
Alex Bennée