KVM: arm/arm64: vgic: Add refcounting for IRQs

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 for
those structures using the kernel's kref infrastructure.
Since private IRQs and SPIs are statically allocated, we avoid actually
refcounting them, since they would never be released anyway.
But we take provisions to increase the refcount when an IRQ gets onto a
VCPU list and decrease it when it gets removed. Also this introduces
vgic_put_irq(), which wraps kref_put and hides the release function from
the callers.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
Tested-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

1 files changed, 24 insertions, 1 deletions

diff --git a/virt/kvm/arm/vgic/vgic-mmio.c b/virt/kvm/arm/vgic/vgic-mmio.c
index 9f6fab74dce7..5e79e0137cb6 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(vcpu->kvm, irq);
 	}
 
 	return value;
@@ -74,6 +76,8 @@ void vgic_mmio_write_senable(struct kvm_vcpu *vcpu,
 		spin_lock(&irq->irq_lock);
 		irq->enabled = true;
 		vgic_queue_irq_unlock(vcpu->kvm, irq);
+
+		vgic_put_irq(vcpu->kvm, irq);
 	}
 }
 
@@ -92,6 +96,7 @@ void vgic_mmio_write_cenable(struct kvm_vcpu *vcpu,
 		irq->enabled = false;
 
 		spin_unlock(&irq->irq_lock);
+		vgic_put_irq(vcpu->kvm, irq);
 	}
 }
 
@@ -108,6 +113,8 @@ unsigned long vgic_mmio_read_pending(struct kvm_vcpu *vcpu,
 
 		if (irq->pending)
 			value |= (1U << i);
+
+		vgic_put_irq(vcpu->kvm, irq);
 	}
 
 	return value;
@@ -129,6 +136,7 @@ void vgic_mmio_write_spending(struct kvm_vcpu *vcpu,
 			irq->soft_pending = true;
 
 		vgic_queue_irq_unlock(vcpu->kvm, irq);
+		vgic_put_irq(vcpu->kvm, irq);
 	}
 }
 
@@ -152,6 +160,7 @@ void vgic_mmio_write_cpending(struct kvm_vcpu *vcpu,
 		}
 
 		spin_unlock(&irq->irq_lock);
+		vgic_put_irq(vcpu->kvm, irq);
 	}
 }
 
@@ -168,6 +177,8 @@ unsigned long vgic_mmio_read_active(struct kvm_vcpu *vcpu,
 
 		if (irq->active)
 			value |= (1U << i);
+
+		vgic_put_irq(vcpu->kvm, irq);
 	}
 
 	return value;
@@ -242,6 +253,7 @@ void vgic_mmio_write_cactive(struct kvm_vcpu *vcpu,
 	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_put_irq(vcpu->kvm, irq);
 	}
 	vgic_change_active_finish(vcpu, intid);
 }
@@ -257,6 +269,7 @@ void vgic_mmio_write_sactive(struct kvm_vcpu *vcpu,
 	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_put_irq(vcpu->kvm, irq);
 	}
 	vgic_change_active_finish(vcpu, intid);
 }
@@ -272,6 +285,8 @@ 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(vcpu->kvm, irq);
 	}
 
 	return val;
@@ -298,6 +313,8 @@ void vgic_mmio_write_priority(struct kvm_vcpu *vcpu,
 		/* 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(vcpu->kvm, irq);
 	}
 }
 
@@ -313,6 +330,8 @@ unsigned long vgic_mmio_read_config(struct kvm_vcpu *vcpu,
 
 		if (irq->config == VGIC_CONFIG_EDGE)
 			value |= (2U << (i * 2));
+
+		vgic_put_irq(vcpu->kvm, irq);
 	}
 
 	return value;
@@ -326,7 +345,7 @@ 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 +356,18 @@ void vgic_mmio_write_config(struct kvm_vcpu *vcpu,
 		if (intid + i < VGIC_NR_PRIVATE_IRQS)
 			continue;
 
+		irq = vgic_get_irq(vcpu->kvm, vcpu, intid + i);
 		spin_lock(&irq->irq_lock);
+
 		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(vcpu->kvm, irq);
 	}
 }