Re: [PATCH] KVM: Fix RTC interrupt coalescing tracking

[Gleb Natapov <gleb@redhat.com>]

On Wed, Jun 26, 2013 at 07:49:37AM +0200, Jan Kiszka wrote:
> On 2013-06-24 14:19, Gleb Natapov wrote:
> > This reverts most of the f1ed0450a5fac7067590317cbf027f566b6ccbca. After
> > the commit kvm_apic_set_irq() no longer returns accurate information
> > about interrupt injection status if injection is done into disabled
> > APIC. RTC interrupt coalescing tracking relies on the information to be
> > accurate and cannot recover if it is not.
> > 
> > Signed-off-by: Gleb Natapov <gleb@redhat.com>
> > diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> > index 9d75193..9f4bea8 100644
> > --- a/arch/x86/kvm/lapic.c
> > +++ b/arch/x86/kvm/lapic.c
> > @@ -405,17 +405,17 @@ int kvm_lapic_find_highest_irr(struct kvm_vcpu *vcpu)
> >  	return highest_irr;
> >  }
> >  
> > -static void __apic_accept_irq(struct kvm_lapic *apic, int delivery_mode,
> > -			      int vector, int level, int trig_mode,
> > -			      unsigned long *dest_map);
> > +static int __apic_accept_irq(struct kvm_lapic *apic, int delivery_mode,
> > +			     int vector, int level, int trig_mode,
> > +			     unsigned long *dest_map);
> 
> I still think __apic_accept_irq should unconditionally inject, and the
> test for acpi_enabled belongs into kvm_apic_set_irq. Why should
> __apic_accept_irq accept non-APIC_DM_FIXED messages if the APIC is off?
> See below for another reason to refactor this part of the interface.
> 
10.4.7.2 Local APIC State After It Has Been Software Disabled

The local APIC will respond normally to INIT, NMI, SMI, and SIPI
messages.

> >  
> > -void kvm_apic_set_irq(struct kvm_vcpu *vcpu, struct kvm_lapic_irq *irq,
> > -		      unsigned long *dest_map)
> > +int kvm_apic_set_irq(struct kvm_vcpu *vcpu, struct kvm_lapic_irq *irq,
> > +		unsigned long *dest_map)
> >  {
> >  	struct kvm_lapic *apic = vcpu->arch.apic;
> >  
> > -	__apic_accept_irq(apic, irq->delivery_mode, irq->vector,
> > -			  irq->level, irq->trig_mode, dest_map);
> > +	return __apic_accept_irq(apic, irq->delivery_mode, irq->vector,
> > +			irq->level, irq->trig_mode, dest_map);
> >  }
> >  
> >  static int pv_eoi_put_user(struct kvm_vcpu *vcpu, u8 val)
> > @@ -608,8 +608,7 @@ bool kvm_irq_delivery_to_apic_fast(struct kvm *kvm, struct kvm_lapic *src,
> >  	*r = -1;
> >  
> >  	if (irq->shorthand == APIC_DEST_SELF) {
> > -		kvm_apic_set_irq(src->vcpu, irq, dest_map);
> > -		*r = 1;
> > +		*r = kvm_apic_set_irq(src->vcpu, irq, dest_map);
> >  		return true;
> >  	}
> >  
> > @@ -654,8 +653,7 @@ bool kvm_irq_delivery_to_apic_fast(struct kvm *kvm, struct kvm_lapic *src,
> >  			continue;
> >  		if (*r < 0)
> >  			*r = 0;
> > -		kvm_apic_set_irq(dst[i]->vcpu, irq, dest_map);
> > -		*r += 1;
> > +		*r += kvm_apic_set_irq(dst[i]->vcpu, irq, dest_map);
> >  	}
> >  
> >  	ret = true;
> > @@ -664,11 +662,15 @@ out:
> >  	return ret;
> >  }
> >  
> > -/* Set an IRQ pending in the lapic. */
> > -static void __apic_accept_irq(struct kvm_lapic *apic, int delivery_mode,
> > -			      int vector, int level, int trig_mode,
> > -			      unsigned long *dest_map)
> > +/*
> > + * Add a pending IRQ into lapic.
> > + * Return 1 if successfully added and 0 if discarded.
> > + */
> > +static int __apic_accept_irq(struct kvm_lapic *apic, int delivery_mode,
> > +			     int vector, int level, int trig_mode,
> > +			     unsigned long *dest_map)
> >  {
> > +	int result = 0;
> >  	struct kvm_vcpu *vcpu = apic->vcpu;
> >  
> >  	switch (delivery_mode) {
> > @@ -682,10 +684,13 @@ static void __apic_accept_irq(struct kvm_lapic *apic, int delivery_mode,
> >  		if (dest_map)
> >  			__set_bit(vcpu->vcpu_id, dest_map);
> >  
> > -		if (kvm_x86_ops->deliver_posted_interrupt)
> > +		if (kvm_x86_ops->deliver_posted_interrupt) {
> > +			result = 1;
> >  			kvm_x86_ops->deliver_posted_interrupt(vcpu, vector);
> > -		else {
> > -			if (apic_test_and_set_irr(vector, apic)) {
> > +		} else {
> > +			result = !apic_test_and_set_irr(vector, apic);
> 
> This part of the revert makes no sense. If deliver_posted_interrupt is
> on, we don't have this feedback anymore, thus we decided to remove it, no?
> 
Agree, but I wanted to do clear revert and fix on top.

> Jan
> 
> > +
> > +			if (!result) {
> >  				if (trig_mode)
> >  					apic_debug("level trig mode repeatedly "
> >  						"for vector %d", vector);
> > @@ -697,7 +702,7 @@ static void __apic_accept_irq(struct kvm_lapic *apic, int delivery_mode,
> >  		}
> >  out:
> >  		trace_kvm_apic_accept_irq(vcpu->vcpu_id, delivery_mode,
> > -					  trig_mode, vector, false);
> > +				trig_mode, vector, !result);
> >  		break;
> >  
> >  	case APIC_DM_REMRD:
> > @@ -709,12 +714,14 @@ out:
> >  		break;
> >  
> >  	case APIC_DM_NMI:
> > +		result = 1;
> >  		kvm_inject_nmi(vcpu);
> >  		kvm_vcpu_kick(vcpu);
> >  		break;
> >  
> >  	case APIC_DM_INIT:
> >  		if (!trig_mode || level) {
> > +			result = 1;
> >  			/* assumes that there are only KVM_APIC_INIT/SIPI */
> >  			apic->pending_events = (1UL << KVM_APIC_INIT);
> >  			/* make sure pending_events is visible before sending
> > @@ -731,6 +738,7 @@ out:
> >  	case APIC_DM_STARTUP:
> >  		apic_debug("SIPI to vcpu %d vector 0x%02x\n",
> >  			   vcpu->vcpu_id, vector);
> > +		result = 1;
> >  		apic->sipi_vector = vector;
> >  		/* make sure sipi_vector is visible for the receiver */
> >  		smp_wmb();
> > @@ -752,6 +760,7 @@ out:
> >  		       delivery_mode);
> >  		break;
> >  	}
> > +	return result;
> >  }
> >  
> >  int kvm_apic_compare_prio(struct kvm_vcpu *vcpu1, struct kvm_vcpu *vcpu2)
> > @@ -1461,7 +1470,7 @@ int apic_has_pending_timer(struct kvm_vcpu *vcpu)
> >  	return 0;
> >  }
> >  
> > -void kvm_apic_local_deliver(struct kvm_lapic *apic, int lvt_type)
> > +int kvm_apic_local_deliver(struct kvm_lapic *apic, int lvt_type)
> >  {
> >  	u32 reg = kvm_apic_get_reg(apic, lvt_type);
> >  	int vector, mode, trig_mode;
> > @@ -1470,8 +1479,10 @@ void kvm_apic_local_deliver(struct kvm_lapic *apic, int lvt_type)
> >  		vector = reg & APIC_VECTOR_MASK;
> >  		mode = reg & APIC_MODE_MASK;
> >  		trig_mode = reg & APIC_LVT_LEVEL_TRIGGER;
> > -		__apic_accept_irq(apic, mode, vector, 1, trig_mode, NULL);
> > +		return __apic_accept_irq(apic, mode, vector, 1, trig_mode,
> > +					NULL);
> >  	}
> > +	return 0;
> >  }
> >  
> >  void kvm_apic_nmi_wd_deliver(struct kvm_vcpu *vcpu)
> > diff --git a/arch/x86/kvm/lapic.h b/arch/x86/kvm/lapic.h
> > index 61a73a0..c730ac9 100644
> > --- a/arch/x86/kvm/lapic.h
> > +++ b/arch/x86/kvm/lapic.h
> > @@ -57,9 +57,9 @@ void kvm_apic_update_tmr(struct kvm_vcpu *vcpu, u32 *tmr);
> >  void kvm_apic_update_irr(struct kvm_vcpu *vcpu, u32 *pir);
> >  int kvm_apic_match_physical_addr(struct kvm_lapic *apic, u16 dest);
> >  int kvm_apic_match_logical_addr(struct kvm_lapic *apic, u8 mda);
> > -void kvm_apic_set_irq(struct kvm_vcpu *vcpu, struct kvm_lapic_irq *irq,
> > -		      unsigned long *dest_map);
> > -void kvm_apic_local_deliver(struct kvm_lapic *apic, int lvt_type);
> > +int kvm_apic_set_irq(struct kvm_vcpu *vcpu, struct kvm_lapic_irq *irq,
> > +		unsigned long *dest_map);
> > +int kvm_apic_local_deliver(struct kvm_lapic *apic, int lvt_type);
> >  
> >  bool kvm_irq_delivery_to_apic_fast(struct kvm *kvm, struct kvm_lapic *src,
> >  		struct kvm_lapic_irq *irq, int *r, unsigned long *dest_map);
> > diff --git a/virt/kvm/irq_comm.c b/virt/kvm/irq_comm.c
> > index ef1817b..e2e6b44 100644
> > --- a/virt/kvm/irq_comm.c
> > +++ b/virt/kvm/irq_comm.c
> > @@ -91,8 +91,7 @@ int kvm_irq_delivery_to_apic(struct kvm *kvm, struct kvm_lapic *src,
> >  		if (!kvm_is_dm_lowest_prio(irq)) {
> >  			if (r < 0)
> >  				r = 0;
> > -			kvm_apic_set_irq(vcpu, irq, dest_map);
> > -			r++;
> > +			r += kvm_apic_set_irq(vcpu, irq, dest_map);
> >  		} else if (kvm_lapic_enabled(vcpu)) {
> >  			if (!lowest)
> >  				lowest = vcpu;
> > @@ -101,10 +100,8 @@ int kvm_irq_delivery_to_apic(struct kvm *kvm, struct kvm_lapic *src,
> >  		}
> >  	}
> >  
> > -	if (lowest) {
> > -		kvm_apic_set_irq(lowest, irq, dest_map);
> > -		r = 1;
> > -	}
> > +	if (lowest)
> > +		r = kvm_apic_set_irq(lowest, irq, dest_map);
> >  
> >  	return r;
> >  }
> > --
> > 			Gleb.
> > 
> 
> 



--
			Gleb.