Re: [PATCH v6 5/5] KVM : VMX: Use posted interrupt to deliver virtual interrupt

[Gleb Natapov <gleb@redhat.com>]

On Fri, Mar 15, 2013 at 09:31:11PM +0800, Yang Zhang wrote:
> From: Yang Zhang <yang.z.zhang@Intel.com>
> 
> If posted interrupt is avaliable, then uses it to inject virtual
> interrupt to guest.
> 
> Signed-off-by: Yang Zhang <yang.z.zhang@Intel.com>
> ---
>  arch/x86/kvm/irq.c   |    3 ++-
>  arch/x86/kvm/lapic.c |   16 +++++++++++++---
>  arch/x86/kvm/lapic.h |    1 +
>  arch/x86/kvm/vmx.c   |   11 +++++++++++
>  arch/x86/kvm/x86.c   |    4 ++++
>  5 files changed, 31 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/x86/kvm/irq.c b/arch/x86/kvm/irq.c
> index 484bc87..5179988 100644
> --- a/arch/x86/kvm/irq.c
> +++ b/arch/x86/kvm/irq.c
> @@ -81,7 +81,8 @@ int kvm_cpu_has_interrupt(struct kvm_vcpu *v)
>  	if (kvm_cpu_has_extint(v))
>  		return 1;
>  
> -	return kvm_apic_has_interrupt(v) != -1;	/* LAPIC */
> +	return (kvm_apic_has_interrupt(v) != -1) ||
> +		kvm_hwapic_has_interrupt(v);
That's incorrect. kvm_cpu_has_interrupt() should return true only it
there is IRR suitable to be injected, not just any IRR.
kvm_apic_has_interrupt() should call kvm_apic_update_irr().

>  }
>  EXPORT_SYMBOL_GPL(kvm_cpu_has_interrupt);
>  
> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> index b3ea50e..46c7310 100644
> --- a/arch/x86/kvm/lapic.c
> +++ b/arch/x86/kvm/lapic.c
> @@ -713,7 +713,10 @@ static int __apic_accept_irq(struct kvm_lapic *apic, int delivery_mode,
>  		} else
>  			apic_clear_vector(vector, apic->regs + APIC_TMR);
>  
> -		result = !apic_test_and_set_irr(vector, apic);
> +		result = 1;
> +		if (!kvm_x86_ops->deliver_posted_interrupt(vcpu, vector))
> +			result = !apic_test_and_set_irr(vector, apic);
> +
>  		trace_kvm_apic_accept_irq(vcpu->vcpu_id, delivery_mode,
>  					  trig_mode, vector, !result);
>  		if (!result) {
> @@ -723,8 +726,10 @@ static int __apic_accept_irq(struct kvm_lapic *apic, int delivery_mode,
>  			break;
>  		}
>  
> -		kvm_make_request(KVM_REQ_EVENT, vcpu);
> -		kvm_vcpu_kick(vcpu);
> +		if (!kvm_x86_ops->vm_has_apicv(vcpu->kvm)) {
> +			kvm_make_request(KVM_REQ_EVENT, vcpu);
> +			kvm_vcpu_kick(vcpu);
> +		}
>  		break;
apicv code and non apicv code are completely different. What's the point
checking for apicv twice here?
Just do:

if (kvm_x86_ops->deliver_posted_interrupt)
	kvm_x86_ops->deliver_posted_interrupt(vcpu, vector)
else {
	result = !apic_test_and_set_irr(vector, apic);
	kvm_make_request(KVM_REQ_EVENT, vcpu);
	kvm_vcpu_kick(vcpu);
}

And set kvm_x86_ops->deliver_posted_interrupt only if apicv is enabled.

Also rearrange patches so that APIC_TMR handling goes before posted
interrupt series.

>  
>  	case APIC_DM_REMRD:
> @@ -1604,6 +1609,11 @@ int kvm_apic_has_interrupt(struct kvm_vcpu *vcpu)
>  	return highest_irr;
>  }
>  
> +bool kvm_hwapic_has_interrupt(struct kvm_vcpu *vcpu)
> +{
> +	return kvm_x86_ops->hwapic_has_interrupt(vcpu);
> +}
> +
>  int kvm_apic_accept_pic_intr(struct kvm_vcpu *vcpu)
>  {
>  	u32 lvt0 = kvm_apic_get_reg(vcpu->arch.apic, APIC_LVT0);
> diff --git a/arch/x86/kvm/lapic.h b/arch/x86/kvm/lapic.h
> index e5327be..c6abc63 100644
> --- a/arch/x86/kvm/lapic.h
> +++ b/arch/x86/kvm/lapic.h
> @@ -37,6 +37,7 @@ int kvm_create_lapic(struct kvm_vcpu *vcpu);
>  void kvm_free_lapic(struct kvm_vcpu *vcpu);
>  
>  int kvm_apic_has_interrupt(struct kvm_vcpu *vcpu);
> +bool kvm_hwapic_has_interrupt(struct kvm_vcpu *vcpu);
>  int kvm_apic_accept_pic_intr(struct kvm_vcpu *vcpu);
>  int kvm_get_apic_interrupt(struct kvm_vcpu *vcpu);
>  void kvm_lapic_reset(struct kvm_vcpu *vcpu);
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 0b5a8ae..48a2239 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -3932,6 +3932,17 @@ static void vmx_posted_intr_clear_on(struct kvm_vcpu *vcpu)
>  	clear_bit(POSTED_INTR_ON, (unsigned long *)&vmx->pi_desc.u.control);
>  }
>  
> +/*
> + * Send interrupt to vcpu via posted interrupt way.
> + * Return false if posted interrupt is not supported and the caller will
> + * roll back to old way(via set vIRR).
> + * Return true if posted interrupt is avalialbe, the interrupt is set
> + * in pir(posted interrupt requests):
> + * 1. If target vcpu is running(non-root mode), send posted interrupt
> + * notification to vcpu and hardware will sync pir to vIRR atomically.
> + * 2. If target vcpu isn't running(root mode), kick it to pick up the
> + * interrupt from pir in next vmentry.
> + */
The comment should go into previous patch. Also I prefer to not check
for posted interrupt inside the callback, but set it to NULL instead.
This way we avoid calling a callback on a hot path needlessly.

>  static bool vmx_deliver_posted_interrupt(struct kvm_vcpu *vcpu, int vector)
>  {
>  	struct vcpu_vmx *vmx = to_vmx(vcpu);
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 0baa90d..0981100 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -2679,6 +2679,7 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
>  static int kvm_vcpu_ioctl_get_lapic(struct kvm_vcpu *vcpu,
>  				    struct kvm_lapic_state *s)
>  {
> +	kvm_x86_ops->sync_pir_to_irr(vcpu);
>  	memcpy(s->regs, vcpu->arch.apic->regs, sizeof *s);
>  
>  	return 0;
> @@ -5699,6 +5700,7 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
>  	}
>  
>  	if (kvm_check_request(KVM_REQ_EVENT, vcpu) || req_int_win) {
> +		kvm_x86_ops->sync_pir_to_irr(vcpu);
>  		inject_pending_event(vcpu);
>  
>  		/* enable NMI/IRQ window open exits if needed */
> @@ -5741,6 +5743,8 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
>  
>  	local_irq_disable();
>  
> +	kvm_x86_ops->posted_intr_clear_on(vcpu);
> +
Why is this separate from pir_to_irr syncing?

>  	if (vcpu->mode == EXITING_GUEST_MODE || vcpu->requests
>  	    || need_resched() || signal_pending(current)) {
>  		vcpu->mode = OUTSIDE_GUEST_MODE;
> -- 
> 1.7.1

--
			Gleb.