Re: [PATCH v6 05/15] KVM: arm/arm64: VGIC: add refcounting for IRQs

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Hi Marc,

On 17/06/16 13:08, Andre Przywara wrote:
> In the moment our struct vgic_irq's are statically allocated at guest
> creation time. So getting a pointer to an IRQ structure is trivial and
> safe. LPIs are more dynamic, they can be mapped and unmapped at any time
> during the guest's _runtime_.
> In preparation for supporting LPIs we introduce reference counting to
> those structures. Since private IRQs and SPIs are statically allocated,
> the reqcount never drops to 0 at the moment, but we increase it when an
> IRQ gets onto a VCPU list and decrease it when it gets removed.
> Also vgic_get_irq() gets changed to take the irq_lock already, this is
> later needed to avoid a race between a potential LPI unmap and the
> window between us getting the pointer and locking the IRQ.
> This introduces vgic_put_irq(), which just does the unlock and makes
> the new locking sequence look more symmetrical.
> This approach deviates from the classical Linux refcounting with using
> atomic_* types and functions, because the users of vgic_get_irq() take
> the irq_lock anyway, so we just use an int and adjust the refcount while
> holding the lock.

As discussed verbally, I am almost done on an implementation that uses
the kernel's kref_* infrastructure to implement the ref-counting, on top
of the existing vgic_irq locking.
Since we consider the atomic inc/dec operations comparably cheap, that
shouldn't sacrifice performance, but will increase readability and
avoids nasty bugs in our own refcounting implementation by using well
tested and reviewed code.

Cheers,
Andre.

> 
> Signed-off-by: Andre Przywara <andre.przywara@xxxxxxx>
> ---
>  include/kvm/vgic/vgic.h          |  1 +
>  virt/kvm/arm/vgic/vgic-init.c    |  2 +
>  virt/kvm/arm/vgic/vgic-mmio-v2.c | 21 +++++------
>  virt/kvm/arm/vgic/vgic-mmio-v3.c | 26 ++++++-------
>  virt/kvm/arm/vgic/vgic-mmio.c    | 55 ++++++++++++++++-----------
>  virt/kvm/arm/vgic/vgic-v2.c      |  4 +-
>  virt/kvm/arm/vgic/vgic-v3.c      |  4 +-
>  virt/kvm/arm/vgic/vgic.c         | 81 +++++++++++++++++++++++++---------------
>  virt/kvm/arm/vgic/vgic.h         |  7 +++-
>  9 files changed, 116 insertions(+), 85 deletions(-)
> 
> diff --git a/include/kvm/vgic/vgic.h b/include/kvm/vgic/vgic.h
> index 2f26f37..e488a369 100644
> --- a/include/kvm/vgic/vgic.h
> +++ b/include/kvm/vgic/vgic.h
> @@ -96,6 +96,7 @@ struct vgic_irq {
>  	bool active;			/* not used for LPIs */
>  	bool enabled;
>  	bool hw;			/* Tied to HW IRQ */
> +	int refcnt;			/* Used only for LPIs */
>  	u32 hwintid;			/* HW INTID number */
>  	union {
>  		u8 targets;			/* GICv2 target VCPUs mask */
> diff --git a/virt/kvm/arm/vgic/vgic-init.c b/virt/kvm/arm/vgic/vgic-init.c
> index 90cae48..c4a8df6 100644
> --- a/virt/kvm/arm/vgic/vgic-init.c
> +++ b/virt/kvm/arm/vgic/vgic-init.c
> @@ -177,6 +177,7 @@ static int kvm_vgic_dist_init(struct kvm *kvm, unsigned int nr_spis)
>  		spin_lock_init(&irq->irq_lock);
>  		irq->vcpu = NULL;
>  		irq->target_vcpu = vcpu0;
> +		irq->refcnt = 1;
>  		if (dist->vgic_model == KVM_DEV_TYPE_ARM_VGIC_V2)
>  			irq->targets = 0;
>  		else
> @@ -211,6 +212,7 @@ static void kvm_vgic_vcpu_init(struct kvm_vcpu *vcpu)
>  		irq->vcpu = NULL;
>  		irq->target_vcpu = vcpu;
>  		irq->targets = 1U << vcpu->vcpu_id;
> +		irq->refcnt = 1;
>  		if (vgic_irq_is_sgi(i)) {
>  			/* SGIs */
>  			irq->enabled = 1;
> diff --git a/virt/kvm/arm/vgic/vgic-mmio-v2.c b/virt/kvm/arm/vgic/vgic-mmio-v2.c
> index a213936..7bb3e94 100644
> --- a/virt/kvm/arm/vgic/vgic-mmio-v2.c
> +++ b/virt/kvm/arm/vgic/vgic-mmio-v2.c
> @@ -97,11 +97,10 @@ static void vgic_mmio_write_sgir(struct kvm_vcpu *source_vcpu,
>  
>  		irq = vgic_get_irq(source_vcpu->kvm, vcpu, intid);
>  
> -		spin_lock(&irq->irq_lock);
>  		irq->pending = true;
>  		irq->source |= 1U << source_vcpu->vcpu_id;
>  
> -		vgic_queue_irq_unlock(source_vcpu->kvm, irq);
> +		vgic_queue_irq_put(source_vcpu->kvm, irq);
>  	}
>  }
>  
> @@ -116,6 +115,8 @@ static unsigned long vgic_mmio_read_target(struct kvm_vcpu *vcpu,
>  		struct vgic_irq *irq = vgic_get_irq(vcpu->kvm, vcpu, intid + i);
>  
>  		val |= (u64)irq->targets << (i * 8);
> +
> +		vgic_put_irq(irq);
>  	}
>  
>  	return val;
> @@ -136,13 +137,11 @@ static void vgic_mmio_write_target(struct kvm_vcpu *vcpu,
>  		struct vgic_irq *irq = vgic_get_irq(vcpu->kvm, NULL, intid + i);
>  		int target;
>  
> -		spin_lock(&irq->irq_lock);
> -
>  		irq->targets = (val >> (i * 8)) & 0xff;
>  		target = irq->targets ? __ffs(irq->targets) : 0;
>  		irq->target_vcpu = kvm_get_vcpu(vcpu->kvm, target);
>  
> -		spin_unlock(&irq->irq_lock);
> +		vgic_put_irq(irq);
>  	}
>  }
>  
> @@ -157,6 +156,8 @@ static unsigned long vgic_mmio_read_sgipend(struct kvm_vcpu *vcpu,
>  		struct vgic_irq *irq = vgic_get_irq(vcpu->kvm, vcpu, intid + i);
>  
>  		val |= (u64)irq->source << (i * 8);
> +
> +		vgic_put_irq(irq);
>  	}
>  	return val;
>  }
> @@ -171,13 +172,11 @@ static void vgic_mmio_write_sgipendc(struct kvm_vcpu *vcpu,
>  	for (i = 0; i < len; i++) {
>  		struct vgic_irq *irq = vgic_get_irq(vcpu->kvm, vcpu, intid + i);
>  
> -		spin_lock(&irq->irq_lock);
> -
>  		irq->source &= ~((val >> (i * 8)) & 0xff);
>  		if (!irq->source)
>  			irq->pending = false;
>  
> -		spin_unlock(&irq->irq_lock);
> +		vgic_put_irq(irq);
>  	}
>  }
>  
> @@ -191,15 +190,13 @@ static void vgic_mmio_write_sgipends(struct kvm_vcpu *vcpu,
>  	for (i = 0; i < len; i++) {
>  		struct vgic_irq *irq = vgic_get_irq(vcpu->kvm, vcpu, intid + i);
>  
> -		spin_lock(&irq->irq_lock);
> -
>  		irq->source |= (val >> (i * 8)) & 0xff;
>  
>  		if (irq->source) {
>  			irq->pending = true;
> -			vgic_queue_irq_unlock(vcpu->kvm, irq);
> +			vgic_queue_irq_put(vcpu->kvm, irq);
>  		} else {
> -			spin_unlock(&irq->irq_lock);
> +			vgic_put_irq(irq);
>  		}
>  	}
>  }
> diff --git a/virt/kvm/arm/vgic/vgic-mmio-v3.c b/virt/kvm/arm/vgic/vgic-mmio-v3.c
> index fc7b6c9..c38302d 100644
> --- a/virt/kvm/arm/vgic/vgic-mmio-v3.c
> +++ b/virt/kvm/arm/vgic/vgic-mmio-v3.c
> @@ -80,15 +80,17 @@ static unsigned long vgic_mmio_read_irouter(struct kvm_vcpu *vcpu,
>  {
>  	int intid = VGIC_ADDR_TO_INTID(addr, 64);
>  	struct vgic_irq *irq = vgic_get_irq(vcpu->kvm, NULL, intid);
> +	unsigned long ret = 0;
>  
>  	if (!irq)
>  		return 0;
>  
>  	/* The upper word is RAZ for us. */
> -	if (addr & 4)
> -		return 0;
> +	if (!(addr & 4))
> +		ret = extract_bytes(READ_ONCE(irq->mpidr), addr & 7, len);
>  
> -	return extract_bytes(READ_ONCE(irq->mpidr), addr & 7, len);
> +	vgic_put_irq(irq);
> +	return ret;
>  }
>  
>  static void vgic_mmio_write_irouter(struct kvm_vcpu *vcpu,
> @@ -102,16 +104,13 @@ static void vgic_mmio_write_irouter(struct kvm_vcpu *vcpu,
>  		return;
>  
>  	/* The upper word is WI for us since we don't implement Aff3. */
> -	if (addr & 4)
> -		return;
> -
> -	spin_lock(&irq->irq_lock);
> -
> -	/* We only care about and preserve Aff0, Aff1 and Aff2. */
> -	irq->mpidr = val & GENMASK(23, 0);
> -	irq->target_vcpu = kvm_mpidr_to_vcpu(vcpu->kvm, irq->mpidr);
> +	if (!(addr & 4)) {
> +		/* We only care about and preserve Aff0, Aff1 and Aff2. */
> +		irq->mpidr = val & GENMASK(23, 0);
> +		irq->target_vcpu = kvm_mpidr_to_vcpu(vcpu->kvm, irq->mpidr);
> +	}
>  
> -	spin_unlock(&irq->irq_lock);
> +	vgic_put_irq(irq);
>  }
>  
>  static unsigned long vgic_mmio_read_v3r_typer(struct kvm_vcpu *vcpu,
> @@ -441,9 +440,8 @@ void vgic_v3_dispatch_sgi(struct kvm_vcpu *vcpu, u64 reg)
>  
>  		irq = vgic_get_irq(vcpu->kvm, c_vcpu, sgi);
>  
> -		spin_lock(&irq->irq_lock);
>  		irq->pending = true;
>  
> -		vgic_queue_irq_unlock(vcpu->kvm, irq);
> +		vgic_queue_irq_put(vcpu->kvm, irq);
>  	}
>  }
> diff --git a/virt/kvm/arm/vgic/vgic-mmio.c b/virt/kvm/arm/vgic/vgic-mmio.c
> index 9f6fab7..4050c1c 100644
> --- a/virt/kvm/arm/vgic/vgic-mmio.c
> +++ b/virt/kvm/arm/vgic/vgic-mmio.c
> @@ -56,6 +56,8 @@ unsigned long vgic_mmio_read_enable(struct kvm_vcpu *vcpu,
>  
>  		if (irq->enabled)
>  			value |= (1U << i);
> +
> +		vgic_put_irq(irq);
>  	}
>  
>  	return value;
> @@ -71,9 +73,9 @@ void vgic_mmio_write_senable(struct kvm_vcpu *vcpu,
>  	for_each_set_bit(i, &val, len * 8) {
>  		struct vgic_irq *irq = vgic_get_irq(vcpu->kvm, vcpu, intid + i);
>  
> -		spin_lock(&irq->irq_lock);
>  		irq->enabled = true;
> -		vgic_queue_irq_unlock(vcpu->kvm, irq);
> +
> +		vgic_queue_irq_put(vcpu->kvm, irq);
>  	}
>  }
>  
> @@ -87,11 +89,9 @@ void vgic_mmio_write_cenable(struct kvm_vcpu *vcpu,
>  	for_each_set_bit(i, &val, len * 8) {
>  		struct vgic_irq *irq = vgic_get_irq(vcpu->kvm, vcpu, intid + i);
>  
> -		spin_lock(&irq->irq_lock);
> -
>  		irq->enabled = false;
>  
> -		spin_unlock(&irq->irq_lock);
> +		vgic_put_irq(irq);
>  	}
>  }
>  
> @@ -108,6 +108,8 @@ unsigned long vgic_mmio_read_pending(struct kvm_vcpu *vcpu,
>  
>  		if (irq->pending)
>  			value |= (1U << i);
> +
> +		vgic_put_irq(irq);
>  	}
>  
>  	return value;
> @@ -123,12 +125,11 @@ void vgic_mmio_write_spending(struct kvm_vcpu *vcpu,
>  	for_each_set_bit(i, &val, len * 8) {
>  		struct vgic_irq *irq = vgic_get_irq(vcpu->kvm, vcpu, intid + i);
>  
> -		spin_lock(&irq->irq_lock);
>  		irq->pending = true;
>  		if (irq->config == VGIC_CONFIG_LEVEL)
>  			irq->soft_pending = true;
>  
> -		vgic_queue_irq_unlock(vcpu->kvm, irq);
> +		vgic_queue_irq_put(vcpu->kvm, irq);
>  	}
>  }
>  
> @@ -142,8 +143,6 @@ void vgic_mmio_write_cpending(struct kvm_vcpu *vcpu,
>  	for_each_set_bit(i, &val, len * 8) {
>  		struct vgic_irq *irq = vgic_get_irq(vcpu->kvm, vcpu, intid + i);
>  
> -		spin_lock(&irq->irq_lock);
> -
>  		if (irq->config == VGIC_CONFIG_LEVEL) {
>  			irq->soft_pending = false;
>  			irq->pending = irq->line_level;
> @@ -151,7 +150,7 @@ void vgic_mmio_write_cpending(struct kvm_vcpu *vcpu,
>  			irq->pending = false;
>  		}
>  
> -		spin_unlock(&irq->irq_lock);
> +		vgic_put_irq(irq);
>  	}
>  }
>  
> @@ -168,15 +167,17 @@ unsigned long vgic_mmio_read_active(struct kvm_vcpu *vcpu,
>  
>  		if (irq->active)
>  			value |= (1U << i);
> +
> +		vgic_put_irq(irq);
>  	}
>  
>  	return value;
>  }
>  
> -static void vgic_mmio_change_active(struct kvm_vcpu *vcpu, struct vgic_irq *irq,
> -				    bool new_active_state)
> +static void vgic_mmio_change_active_put(struct kvm_vcpu *vcpu,
> +					struct vgic_irq *irq,
> +					bool new_active_state)
>  {
> -	spin_lock(&irq->irq_lock);
>  	/*
>  	 * If this virtual IRQ was written into a list register, we
>  	 * have to make sure the CPU that runs the VCPU thread has
> @@ -190,15 +191,17 @@ static void vgic_mmio_change_active(struct kvm_vcpu *vcpu, struct vgic_irq *irq,
>  	 * IRQ, so we release and re-acquire the spin_lock to let the
>  	 * other thread sync back the IRQ.
>  	 */
> +	irq->refcnt++;
>  	while (irq->vcpu && /* IRQ may have state in an LR somewhere */
>  	       irq->vcpu->cpu != -1) /* VCPU thread is running */
>  		cond_resched_lock(&irq->irq_lock);
>  
> +	irq->refcnt--;
>  	irq->active = new_active_state;
>  	if (new_active_state)
> -		vgic_queue_irq_unlock(vcpu->kvm, irq);
> +		vgic_queue_irq_put(vcpu->kvm, irq);
>  	else
> -		spin_unlock(&irq->irq_lock);
> +		vgic_put_irq(irq);
>  }
>  
>  /*
> @@ -241,7 +244,8 @@ void vgic_mmio_write_cactive(struct kvm_vcpu *vcpu,
>  	vgic_change_active_prepare(vcpu, intid);
>  	for_each_set_bit(i, &val, len * 8) {
>  		struct vgic_irq *irq = vgic_get_irq(vcpu->kvm, vcpu, intid + i);
> -		vgic_mmio_change_active(vcpu, irq, false);
> +
> +		vgic_mmio_change_active_put(vcpu, irq, false);
>  	}
>  	vgic_change_active_finish(vcpu, intid);
>  }
> @@ -256,7 +260,8 @@ void vgic_mmio_write_sactive(struct kvm_vcpu *vcpu,
>  	vgic_change_active_prepare(vcpu, intid);
>  	for_each_set_bit(i, &val, len * 8) {
>  		struct vgic_irq *irq = vgic_get_irq(vcpu->kvm, vcpu, intid + i);
> -		vgic_mmio_change_active(vcpu, irq, true);
> +
> +		vgic_mmio_change_active_put(vcpu, irq, true);
>  	}
>  	vgic_change_active_finish(vcpu, intid);
>  }
> @@ -272,6 +277,8 @@ unsigned long vgic_mmio_read_priority(struct kvm_vcpu *vcpu,
>  		struct vgic_irq *irq = vgic_get_irq(vcpu->kvm, vcpu, intid + i);
>  
>  		val |= (u64)irq->priority << (i * 8);
> +
> +		vgic_put_irq(irq);
>  	}
>  
>  	return val;
> @@ -294,10 +301,10 @@ void vgic_mmio_write_priority(struct kvm_vcpu *vcpu,
>  	for (i = 0; i < len; i++) {
>  		struct vgic_irq *irq = vgic_get_irq(vcpu->kvm, vcpu, intid + i);
>  
> -		spin_lock(&irq->irq_lock);
>  		/* Narrow the priority range to what we actually support */
>  		irq->priority = (val >> (i * 8)) & GENMASK(7, 8 - VGIC_PRI_BITS);
> -		spin_unlock(&irq->irq_lock);
> +
> +		vgic_put_irq(irq);
>  	}
>  }
>  
> @@ -313,6 +320,8 @@ unsigned long vgic_mmio_read_config(struct kvm_vcpu *vcpu,
>  
>  		if (irq->config == VGIC_CONFIG_EDGE)
>  			value |= (2U << (i * 2));
> +
> +		vgic_put_irq(irq);
>  	}
>  
>  	return value;
> @@ -326,7 +335,7 @@ void vgic_mmio_write_config(struct kvm_vcpu *vcpu,
>  	int i;
>  
>  	for (i = 0; i < len * 4; i++) {
> -		struct vgic_irq *irq = vgic_get_irq(vcpu->kvm, vcpu, intid + i);
> +		struct vgic_irq *irq;
>  
>  		/*
>  		 * The configuration cannot be changed for SGIs in general,
> @@ -337,14 +346,16 @@ void vgic_mmio_write_config(struct kvm_vcpu *vcpu,
>  		if (intid + i < VGIC_NR_PRIVATE_IRQS)
>  			continue;
>  
> -		spin_lock(&irq->irq_lock);
> +		irq = vgic_get_irq(vcpu->kvm, vcpu, intid + i);
> +
>  		if (test_bit(i * 2 + 1, &val)) {
>  			irq->config = VGIC_CONFIG_EDGE;
>  		} else {
>  			irq->config = VGIC_CONFIG_LEVEL;
>  			irq->pending = irq->line_level | irq->soft_pending;
>  		}
> -		spin_unlock(&irq->irq_lock);
> +
> +		vgic_put_irq(irq);
>  	}
>  }
>  
> diff --git a/virt/kvm/arm/vgic/vgic-v2.c b/virt/kvm/arm/vgic/vgic-v2.c
> index 80313de..2147576 100644
> --- a/virt/kvm/arm/vgic/vgic-v2.c
> +++ b/virt/kvm/arm/vgic/vgic-v2.c
> @@ -94,8 +94,6 @@ void vgic_v2_fold_lr_state(struct kvm_vcpu *vcpu)
>  
>  		irq = vgic_get_irq(vcpu->kvm, vcpu, intid);
>  
> -		spin_lock(&irq->irq_lock);
> -
>  		/* Always preserve the active bit */
>  		irq->active = !!(val & GICH_LR_ACTIVE_BIT);
>  
> @@ -123,7 +121,7 @@ void vgic_v2_fold_lr_state(struct kvm_vcpu *vcpu)
>  			irq->pending = irq->line_level || irq->soft_pending;
>  		}
>  
> -		spin_unlock(&irq->irq_lock);
> +		vgic_put_irq(irq);
>  	}
>  }
>  
> diff --git a/virt/kvm/arm/vgic/vgic-v3.c b/virt/kvm/arm/vgic/vgic-v3.c
> index e48a22e..21d84e9 100644
> --- a/virt/kvm/arm/vgic/vgic-v3.c
> +++ b/virt/kvm/arm/vgic/vgic-v3.c
> @@ -82,8 +82,6 @@ void vgic_v3_fold_lr_state(struct kvm_vcpu *vcpu)
>  			intid = val & GICH_LR_VIRTUALID;
>  		irq = vgic_get_irq(vcpu->kvm, vcpu, intid);
>  
> -		spin_lock(&irq->irq_lock);
> -
>  		/* Always preserve the active bit */
>  		irq->active = !!(val & ICH_LR_ACTIVE_BIT);
>  
> @@ -112,7 +110,7 @@ void vgic_v3_fold_lr_state(struct kvm_vcpu *vcpu)
>  			irq->pending = irq->line_level || irq->soft_pending;
>  		}
>  
> -		spin_unlock(&irq->irq_lock);
> +		vgic_put_irq(irq);
>  	}
>  }
>  
> diff --git a/virt/kvm/arm/vgic/vgic.c b/virt/kvm/arm/vgic/vgic.c
> index 69b61ab..90f2543 100644
> --- a/virt/kvm/arm/vgic/vgic.c
> +++ b/virt/kvm/arm/vgic/vgic.c
> @@ -48,13 +48,20 @@ struct vgic_global __section(.hyp.text) kvm_vgic_global_state;
>  struct vgic_irq *vgic_get_irq(struct kvm *kvm, struct kvm_vcpu *vcpu,
>  			      u32 intid)
>  {
> -	/* SGIs and PPIs */
> -	if (intid <= VGIC_MAX_PRIVATE)
> -		return &vcpu->arch.vgic_cpu.private_irqs[intid];
> +	struct vgic_dist *dist = &kvm->arch.vgic;
> +	struct vgic_irq *irq;
>  
> -	/* SPIs */
> -	if (intid <= VGIC_MAX_SPI)
> -		return &kvm->arch.vgic.spis[intid - VGIC_NR_PRIVATE_IRQS];
> +	if (intid <= VGIC_MAX_PRIVATE) {        /* SGIs and PPIs */
> +		irq = &vcpu->arch.vgic_cpu.private_irqs[intid];
> +		spin_lock(&irq->irq_lock);
> +		return irq;
> +	}
> +
> +	if (intid <= VGIC_MAX_SPI) {            /* SPIs */
> +		irq = &dist->spis[intid - VGIC_NR_PRIVATE_IRQS];
> +		spin_lock(&irq->irq_lock);
> +		return irq;
> +	}
>  
>  	/* LPIs are not yet covered */
>  	if (intid >= VGIC_MIN_LPI)
> @@ -183,9 +190,10 @@ static bool vgic_validate_injection(struct vgic_irq *irq, bool level)
>   * Needs to be entered with the IRQ lock already held, but will return
>   * with all locks dropped.
>   */
> -bool vgic_queue_irq_unlock(struct kvm *kvm, struct vgic_irq *irq)
> +bool vgic_queue_irq_put(struct kvm *kvm, struct vgic_irq *irq)
>  {
> -	struct kvm_vcpu *vcpu;
> +	struct kvm_vcpu *vcpu, *irq_vcpu = irq->target_vcpu;
> +	u32 intid = irq->intid;
>  
>  	DEBUG_SPINLOCK_BUG_ON(!spin_is_locked(&irq->irq_lock));
>  
> @@ -201,7 +209,7 @@ retry:
>  		 * not need to be inserted into an ap_list and there is also
>  		 * no more work for us to do.
>  		 */
> -		spin_unlock(&irq->irq_lock);
> +		vgic_put_irq(irq);
>  		return false;
>  	}
>  
> @@ -209,12 +217,18 @@ retry:
>  	 * We must unlock the irq lock to take the ap_list_lock where
>  	 * we are going to insert this new pending interrupt.
>  	 */
> -	spin_unlock(&irq->irq_lock);
> +	vgic_put_irq(irq);
>  
>  	/* someone can do stuff here, which we re-check below */
>  
>  	spin_lock(&vcpu->arch.vgic_cpu.ap_list_lock);
> -	spin_lock(&irq->irq_lock);
> +	irq = vgic_get_irq(kvm, irq_vcpu, intid);
> +
> +	if (!irq) {
> +		/* The LPI has been unmapped, nothing left to do. */
> +		spin_unlock(&vcpu->arch.vgic_cpu.ap_list_lock);
> +		return false;
> +	}
>  
>  	/*
>  	 * Did something change behind our backs?
> @@ -229,17 +243,21 @@ retry:
>  	 */
>  
>  	if (unlikely(irq->vcpu || vcpu != vgic_target_oracle(irq))) {
> -		spin_unlock(&irq->irq_lock);
> +		vgic_put_irq(irq);
>  		spin_unlock(&vcpu->arch.vgic_cpu.ap_list_lock);
>  
> -		spin_lock(&irq->irq_lock);
> +		irq = vgic_get_irq(kvm, irq_vcpu, intid);
> +		if (!irq)
> +			return false;
> +
>  		goto retry;
>  	}
>  
>  	list_add_tail(&irq->ap_list, &vcpu->arch.vgic_cpu.ap_list_head);
> +	irq->refcnt++;
>  	irq->vcpu = vcpu;
>  
> -	spin_unlock(&irq->irq_lock);
> +	vgic_put_irq(irq);
>  	spin_unlock(&vcpu->arch.vgic_cpu.ap_list_lock);
>  
>  	kvm_vcpu_kick(vcpu);
> @@ -269,14 +287,14 @@ static int vgic_update_irq_pending(struct kvm *kvm, int cpuid,
>  	if (!irq)
>  		return -EINVAL;
>  
> -	if (irq->hw != mapped_irq)
> +	if (irq->hw != mapped_irq) {
> +		vgic_put_irq(irq);
>  		return -EINVAL;
> -
> -	spin_lock(&irq->irq_lock);
> +	}
>  
>  	if (!vgic_validate_injection(irq, level)) {
>  		/* Nothing to see here, move along... */
> -		spin_unlock(&irq->irq_lock);
> +		vgic_put_irq(irq);
>  		return 0;
>  	}
>  
> @@ -287,7 +305,7 @@ static int vgic_update_irq_pending(struct kvm *kvm, int cpuid,
>  		irq->pending = true;
>  	}
>  
> -	vgic_queue_irq_unlock(kvm, irq);
> +	vgic_queue_irq_put(kvm, irq);
>  
>  	return 0;
>  }
> @@ -324,31 +342,28 @@ int kvm_vgic_map_phys_irq(struct kvm_vcpu *vcpu, u32 virt_irq, u32 phys_irq)
>  
>  	BUG_ON(!irq);
>  
> -	spin_lock(&irq->irq_lock);
> -
>  	irq->hw = true;
>  	irq->hwintid = phys_irq;
>  
> -	spin_unlock(&irq->irq_lock);
> +	vgic_put_irq(irq);
>  
>  	return 0;
>  }
>  
>  int kvm_vgic_unmap_phys_irq(struct kvm_vcpu *vcpu, unsigned int virt_irq)
>  {
> -	struct vgic_irq *irq = vgic_get_irq(vcpu->kvm, vcpu, virt_irq);
> -
> -	BUG_ON(!irq);
> +	struct vgic_irq *irq;
>  
>  	if (!vgic_initialized(vcpu->kvm))
>  		return -EAGAIN;
>  
> -	spin_lock(&irq->irq_lock);
> +	irq = vgic_get_irq(vcpu->kvm, vcpu, virt_irq);
> +	BUG_ON(!irq);
>  
>  	irq->hw = false;
>  	irq->hwintid = 0;
>  
> -	spin_unlock(&irq->irq_lock);
> +	vgic_put_irq(irq);
>  
>  	return 0;
>  }
> @@ -378,14 +393,21 @@ retry:
>  
>  		target_vcpu = vgic_target_oracle(irq);
>  
> -		if (!target_vcpu) {
> +		if (!target_vcpu || irq->refcnt == 1) {
> +			bool free_irq = false;
> +
>  			/*
>  			 * We don't need to process this interrupt any
>  			 * further, move it off the list.
>  			 */
>  			list_del(&irq->ap_list);
>  			irq->vcpu = NULL;
> +			irq->refcnt--;
> +			if (!irq->refcnt)
> +				free_irq = true;
>  			spin_unlock(&irq->irq_lock);
> +			if (free_irq)
> +				kfree(irq);
>  			continue;
>  		}
>  
> @@ -611,9 +633,8 @@ bool kvm_vgic_map_is_active(struct kvm_vcpu *vcpu, unsigned int virt_irq)
>  	struct vgic_irq *irq = vgic_get_irq(vcpu->kvm, vcpu, virt_irq);
>  	bool map_is_active;
>  
> -	spin_lock(&irq->irq_lock);
>  	map_is_active = irq->hw && irq->active;
> -	spin_unlock(&irq->irq_lock);
> +	vgic_put_irq(irq);
>  
>  	return map_is_active;
>  }
> diff --git a/virt/kvm/arm/vgic/vgic.h b/virt/kvm/arm/vgic/vgic.h
> index c752152..fa2d225 100644
> --- a/virt/kvm/arm/vgic/vgic.h
> +++ b/virt/kvm/arm/vgic/vgic.h
> @@ -38,7 +38,12 @@ struct vgic_vmcr {
>  
>  struct vgic_irq *vgic_get_irq(struct kvm *kvm, struct kvm_vcpu *vcpu,
>  			      u32 intid);
> -bool vgic_queue_irq_unlock(struct kvm *kvm, struct vgic_irq *irq);
> +static inline void vgic_put_irq(struct vgic_irq *irq)
> +{
> +	spin_unlock(&irq->irq_lock);
> +}
> +
> +bool vgic_queue_irq_put(struct kvm *kvm, struct vgic_irq *irq);
>  void vgic_kick_vcpus(struct kvm *kvm);
>  
>  void vgic_v2_process_maintenance(struct kvm_vcpu *vcpu);
> 
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