[PATCH 21/22] KVM: vgic-v4: Track the number of VLPIs per vcpu

[Marc Zyngier <maz@kernel.org>]

In order to find out whether a vcpu is likely to be the target of
VLPIs (and to further optimize the way we deal with those), let's
track the number of VLPIs a vcpu can receive.

This gets implemented with an atomic variable that gets incremented
or decremented on map, unmap and move of a VLPI.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Zenghui Yu <yuzenghui@huawei.com>
Reviewed-by: Christoffer Dall <christoffer.dall@arm.com>
Link: https://lore.kernel.org/r/20191107160412.30301-2-maz@kernel.org
---
 include/linux/irqchip/arm-gic-v4.h | 2 ++
 virt/kvm/arm/vgic/vgic-init.c      | 1 +
 virt/kvm/arm/vgic/vgic-its.c       | 3 +++
 virt/kvm/arm/vgic/vgic-v4.c        | 2 ++
 4 files changed, 8 insertions(+)

diff --git a/include/linux/irqchip/arm-gic-v4.h b/include/linux/irqchip/arm-gic-v4.h
index ab1396afe08a..5dbcfc65f21e 100644
--- a/include/linux/irqchip/arm-gic-v4.h
+++ b/include/linux/irqchip/arm-gic-v4.h
@@ -32,6 +32,8 @@ struct its_vm {
 struct its_vpe {
 	struct page 		*vpt_page;
 	struct its_vm		*its_vm;
+	/* per-vPE VLPI tracking */
+	atomic_t		vlpi_count;
 	/* Doorbell interrupt */
 	int			irq;
 	irq_hw_number_t		vpe_db_lpi;
diff --git a/virt/kvm/arm/vgic/vgic-init.c b/virt/kvm/arm/vgic/vgic-init.c
index 6f50c429196d..b3c5de48064c 100644
--- a/virt/kvm/arm/vgic/vgic-init.c
+++ b/virt/kvm/arm/vgic/vgic-init.c
@@ -203,6 +203,7 @@ int kvm_vgic_vcpu_init(struct kvm_vcpu *vcpu)
 
 	INIT_LIST_HEAD(&vgic_cpu->ap_list_head);
 	raw_spin_lock_init(&vgic_cpu->ap_list_lock);
+	atomic_set(&vgic_cpu->vgic_v3.its_vpe.vlpi_count, 0);
 
 	/*
 	 * Enable and configure all SGIs to be edge-triggered and
diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c
index 2be6b66b3856..98c7360d9fb7 100644
--- a/virt/kvm/arm/vgic/vgic-its.c
+++ b/virt/kvm/arm/vgic/vgic-its.c
@@ -360,7 +360,10 @@ static int update_affinity(struct vgic_irq *irq, struct kvm_vcpu *vcpu)
 		if (ret)
 			return ret;
 
+		if (map.vpe)
+			atomic_dec(&map.vpe->vlpi_count);
 		map.vpe = &vcpu->arch.vgic_cpu.vgic_v3.its_vpe;
+		atomic_inc(&map.vpe->vlpi_count);
 
 		ret = its_map_vlpi(irq->host_irq, &map);
 	}
diff --git a/virt/kvm/arm/vgic/vgic-v4.c b/virt/kvm/arm/vgic/vgic-v4.c
index 0965fb0c427a..46f875589c47 100644
--- a/virt/kvm/arm/vgic/vgic-v4.c
+++ b/virt/kvm/arm/vgic/vgic-v4.c
@@ -309,6 +309,7 @@ int kvm_vgic_v4_set_forwarding(struct kvm *kvm, int virq,
 
 	irq->hw		= true;
 	irq->host_irq	= virq;
+	atomic_inc(&map.vpe->vlpi_count);
 
 out:
 	mutex_unlock(&its->its_lock);
@@ -342,6 +343,7 @@ int kvm_vgic_v4_unset_forwarding(struct kvm *kvm, int virq,
 
 	WARN_ON(!(irq->hw && irq->host_irq == virq));
 	if (irq->hw) {
+		atomic_dec(&irq->target_vcpu->arch.vgic_cpu.vgic_v3.its_vpe.vlpi_count);
 		irq->hw = false;
 		ret = its_unmap_vlpi(virq);
 	}
-- 
2.20.1