linux-kernel - Re: [PART1 RFC 6/9] svm: Add interrupt injection via AVIC

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Date:	Fri, 12 Feb 2016 16:55:09 +0100
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	Suravee Suthikulpanit <suravee.suthikulpanit@....com>,
	joro@...tes.org, alex.williamson@...hat.com, gleb@...nel.org
Cc:	kvm@...r.kernel.org, linux-kernel@...r.kernel.org, wei@...hat.com,
	sherry.hurwitz@....com
Subject: Re: [PART1 RFC 6/9] svm: Add interrupt injection via AVIC



On 12/02/2016 14:59, Suravee Suthikulpanit wrote:
> +static bool avic_check_irr_pending(struct kvm_vcpu *vcpu)
> +{
> +	int i;
> +	u32 irr;
> +	struct vcpu_svm *svm = to_svm(vcpu);
> +
> +	for (i = 0; i < 8; i++) {
> +		irr = *(avic_get_bk_page_entry(svm,
> +					APIC_IRR + (0x10 * i)));
> +		if (irr)
> +			return true;
> +	}
> +
> +	return false;
> +}
> +
> +static bool svm_avic_check_ppr(struct vcpu_svm *svm)
> +{
> +	u32 tpr = *(avic_get_bk_page_entry(svm, APIC_TASKPRI));
> +	u32 ppr = *(avic_get_bk_page_entry(svm, APIC_PROCPRI));
> +
> +	if (ppr && (ppr != tpr))
> +		return true;
> +
> +	return false;
> +}
> +
> +/* Note: Returns true means do not block */
> +static bool svm_apicv_intr_pending (struct kvm_vcpu *vcpu)
> +{
> +	struct vcpu_svm *svm = to_svm(vcpu);
> +
> +	if (!avic)
> +		return false;
> +
> +	if (atomic_read(&svm->avic_pending_cnt))
> +		return true;
> +
> +	return avic_check_irr_pending(vcpu);
> +}
> +
> +static void avic_post_vmrun(struct kvm_vcpu *vcpu)
> +{
> +	struct vcpu_svm *svm = to_svm(vcpu);
> +
> +	if (!avic)
> +		return;
> +
> +	if (atomic_read(&svm->avic_pending_cnt)) {
> +		if (svm_avic_check_ppr(svm))
> +			return;
> +		if (avic_check_irr_pending(vcpu))
> +			return;
> +		/*
> +		 * At this point, if there is no interrupt pending.
> +		 * So, we decrement the pending count
> +		 */
> +		atomic_dec(&svm->avic_pending_cnt);
> +	}
> +}
> +
>  static void svm_vcpu_run(struct kvm_vcpu *vcpu)
>  {
>  	struct vcpu_svm *svm = to_svm(vcpu);
> @@ -4588,6 +4686,8 @@ static void svm_vcpu_run(struct kvm_vcpu *vcpu)
>  	if (unlikely(svm->vmcb->control.exit_code == SVM_EXIT_NMI))
>  		kvm_after_handle_nmi(&svm->vcpu);
>  
> +	avic_post_vmrun(vcpu);
> +
>  	sync_cr8_to_lapic(vcpu);
>  
>  	svm->next_rip = 0;
> @@ -5050,7 +5150,9 @@ static struct kvm_x86_ops svm_x86_ops = {
>  
>  	.sched_in = svm_sched_in,
>  
> +	.apicv_intr_pending = svm_apicv_intr_pending,
>  	.pmu_ops = &amd_pmu_ops,
> +	.deliver_posted_interrupt = svm_deliver_avic_intr,
>  };
>  
>  static int __init svm_init(void)
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 4244c2b..2def290 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -8087,7 +8087,9 @@ int kvm_arch_vcpu_runnable(struct kvm_vcpu *vcpu)
>  	if (is_guest_mode(vcpu) && kvm_x86_ops->check_nested_events)
>  		kvm_x86_ops->check_nested_events(vcpu, false);
>  
> -	return kvm_vcpu_running(vcpu) || kvm_vcpu_has_events(vcpu);
> +	return (kvm_vcpu_running(vcpu) || kvm_vcpu_has_events(vcpu) ||
> +		(kvm_x86_ops->apicv_intr_pending &&
> +		 kvm_x86_ops->apicv_intr_pending(vcpu)));
>  }

I think this is not necessary.  What you need is to make kvm_lapic's
regs field point to the backing page.  Then when the processor writes to
IRR, kvm_apic_has_interrupt (called through kvm_vcpu_has_events) will
see it.

avic_pending_cnt shouldn't be necessary either.

Paolo