Re: [PATCH] KVM: pit: Do not check pending pit timer in vcpu thread

[Zachary Amsden <zamsden@redhat.com>]

On 08/26/2010 11:15 PM, Jason Wang wrote:
> Pit interrupt injection was done by workqueue, so no need to check
> pending pit timer in vcpu thread which could lead unnecessary
> unblocking of vcpu.
>    

Is this actually correct?  There were a bunch of workarounds and fixes 
put into this code over time.  Please check with Chris Lalancette, I 
think he was the last to touch this code.

> Signed-off-by: Jason Wang<jasowang@redhat.com>
> ---
>   arch/x86/kvm/i8254.c |    9 ---------
>   arch/x86/kvm/irq.c   |    7 +------
>   2 files changed, 1 insertions(+), 15 deletions(-)
>
> diff --git a/arch/x86/kvm/i8254.c b/arch/x86/kvm/i8254.c
> index ddeb231..2ad40a4 100644
> --- a/arch/x86/kvm/i8254.c
> +++ b/arch/x86/kvm/i8254.c
> @@ -232,15 +232,6 @@ static void pit_latch_status(struct kvm *kvm, int channel)
>   	}
>   }
>
> -int pit_has_pending_timer(struct kvm_vcpu *vcpu)
> -{
> -	struct kvm_pit *pit = vcpu->kvm->arch.vpit;
> -
> -	if (pit&&  kvm_vcpu_is_bsp(vcpu)&&  pit->pit_state.irq_ack)
> -		return atomic_read(&pit->pit_state.pit_timer.pending);
> -	return 0;
> -}
> -
>   static void kvm_pit_ack_irq(struct kvm_irq_ack_notifier *kian)
>   {
>   	struct kvm_kpit_state *ps = container_of(kian, struct kvm_kpit_state,
> diff --git a/arch/x86/kvm/irq.c b/arch/x86/kvm/irq.c
> index 2095a04..f994da4 100644
> --- a/arch/x86/kvm/irq.c
> +++ b/arch/x86/kvm/irq.c
> @@ -33,12 +33,7 @@
>    */
>   int kvm_cpu_has_pending_timer(struct kvm_vcpu *vcpu)
>   {
> -	int ret;
> -
> -	ret = pit_has_pending_timer(vcpu);
> -	ret |= apic_has_pending_timer(vcpu);
> -
> -	return ret;
> +	return apic_has_pending_timer(vcpu);
>   }
>   EXPORT_SYMBOL(kvm_cpu_has_pending_timer);
>
>
> --
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