KVM: arm64: vgic: Split out mapping IRQs and setting irq_ops

Prior to this change, the act of mapping a virtual IRQ to a physical
one also set the irq_ops. Unmapping then reset the irq_ops to NULL. So
far, this has been fine and hasn't caused any major issues.

Now, however, as GICv5 support is being added to KVM, it has become
apparent that conflating mapping/unmapping IRQs and setting/clearing
irq_ops can cause issues. The reason is that the upcoming GICv5
support introduces a set of default irq_ops for PPIs, and removing
this when unmapping will cause things to break rather horribly.

Split out the mapping/unmapping of IRQs from the setting/clearing of
irq_ops. The arch timer code is updated to set the irq_ops following a
successful map. The irq_ops are intentionally not removed again on an
unmap as the only irq_op introduced by the arch timer only takes
effect if the hw bit in struct vgic_irq is set. Therefore, it is safe
to leave this in place, and it avoids additional complexity when GICv5
support is introduced.

Signed-off-by: Sascha Bischoff <sascha.bischoff@arm.com>
Link: https://patch.msgid.link/20260319154937.3619520-6-sascha.bischoff@arm.com
Signed-off-by: Marc Zyngier <maz@kernel.org>

3 files changed, 36 insertions, 18 deletions

diff --git a/arch/arm64/kvm/arch_timer.c b/arch/arm64/kvm/arch_timer.c
index 600f250753b4..d31bc1e7a13c 100644
--- a/arch/arm64/kvm/arch_timer.c
+++ b/arch/arm64/kvm/arch_timer.c
@@ -740,13 +740,11 @@ static void kvm_timer_vcpu_load_nested_switch(struct kvm_vcpu *vcpu,
 
 		ret = kvm_vgic_map_phys_irq(vcpu,
 					    map->direct_vtimer->host_timer_irq,
-					    timer_irq(map->direct_vtimer),
-					    &arch_timer_irq_ops);
+					    timer_irq(map->direct_vtimer));
 		WARN_ON_ONCE(ret);
 		ret = kvm_vgic_map_phys_irq(vcpu,
 					    map->direct_ptimer->host_timer_irq,
-					    timer_irq(map->direct_ptimer),
-					    &arch_timer_irq_ops);
+					    timer_irq(map->direct_ptimer));
 		WARN_ON_ONCE(ret);
 	}
 }
@@ -1543,6 +1541,7 @@ int kvm_timer_enable(struct kvm_vcpu *vcpu)
 {
 	struct arch_timer_cpu *timer = vcpu_timer(vcpu);
 	struct timer_map map;
+	struct irq_ops *ops;
 	int ret;
 
 	if (timer->enabled)
@@ -1563,20 +1562,21 @@ int kvm_timer_enable(struct kvm_vcpu *vcpu)
 
 	get_timer_map(vcpu, &map);
 
+	ops = &arch_timer_irq_ops;
+
+	for (int i = 0; i < nr_timers(vcpu); i++)
+		kvm_vgic_set_irq_ops(vcpu, timer_irq(vcpu_get_timer(vcpu, i)), ops);
+
 	ret = kvm_vgic_map_phys_irq(vcpu,
 				    map.direct_vtimer->host_timer_irq,
-				    timer_irq(map.direct_vtimer),
-				    &arch_timer_irq_ops);
+				    timer_irq(map.direct_vtimer));
 	if (ret)
 		return ret;
 
-	if (map.direct_ptimer) {
+	if (map.direct_ptimer)
 		ret = kvm_vgic_map_phys_irq(vcpu,
 					    map.direct_ptimer->host_timer_irq,
-					    timer_irq(map.direct_ptimer),
-					    &arch_timer_irq_ops);
-	}
-
+					    timer_irq(map.direct_ptimer));
 	if (ret)
 		return ret;
 
diff --git a/arch/arm64/kvm/vgic/vgic.c b/arch/arm64/kvm/vgic/vgic.c
index e22b79cfff96..9e0d26348a2a 100644
--- a/arch/arm64/kvm/vgic/vgic.c
+++ b/arch/arm64/kvm/vgic/vgic.c
@@ -553,10 +553,27 @@ int kvm_vgic_inject_irq(struct kvm *kvm, struct kvm_vcpu *vcpu,
 	return 0;
 }
 
+void kvm_vgic_set_irq_ops(struct kvm_vcpu *vcpu, u32 vintid,
+			  struct irq_ops *ops)
+{
+	struct vgic_irq *irq = vgic_get_vcpu_irq(vcpu, vintid);
+
+	BUG_ON(!irq);
+
+	scoped_guard(raw_spinlock_irqsave, &irq->irq_lock)
+		irq->ops = ops;
+
+	vgic_put_irq(vcpu->kvm, irq);
+}
+
+void kvm_vgic_clear_irq_ops(struct kvm_vcpu *vcpu, u32 vintid)
+{
+	kvm_vgic_set_irq_ops(vcpu, vintid, NULL);
+}
+
 /* @irq->irq_lock must be held */
 static int kvm_vgic_map_irq(struct kvm_vcpu *vcpu, struct vgic_irq *irq,
-			    unsigned int host_irq,
-			    struct irq_ops *ops)
+			    unsigned int host_irq)
 {
 	struct irq_desc *desc;
 	struct irq_data *data;
@@ -576,7 +593,6 @@ static int kvm_vgic_map_irq(struct kvm_vcpu *vcpu, struct vgic_irq *irq,
 	irq->hw = true;
 	irq->host_irq = host_irq;
 	irq->hwintid = data->hwirq;
-	irq->ops = ops;
 	return 0;
 }
 
@@ -585,11 +601,10 @@ static inline void kvm_vgic_unmap_irq(struct vgic_irq *irq)
 {
 	irq->hw = false;
 	irq->hwintid = 0;
-	irq->ops = NULL;
 }
 
 int kvm_vgic_map_phys_irq(struct kvm_vcpu *vcpu, unsigned int host_irq,
-			  u32 vintid, struct irq_ops *ops)
+			  u32 vintid)
 {
 	struct vgic_irq *irq = vgic_get_vcpu_irq(vcpu, vintid);
 	unsigned long flags;
@@ -598,7 +613,7 @@ int kvm_vgic_map_phys_irq(struct kvm_vcpu *vcpu, unsigned int host_irq,
 	BUG_ON(!irq);
 
 	raw_spin_lock_irqsave(&irq->irq_lock, flags);
-	ret = kvm_vgic_map_irq(vcpu, irq, host_irq, ops);
+	ret = kvm_vgic_map_irq(vcpu, irq, host_irq);
 	raw_spin_unlock_irqrestore(&irq->irq_lock, flags);
 	vgic_put_irq(vcpu->kvm, irq);
 
diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
index f2eafc65bbf4..46262d1433bc 100644
--- a/include/kvm/arm_vgic.h
+++ b/include/kvm/arm_vgic.h
@@ -397,8 +397,11 @@ void kvm_vgic_init_cpu_hardware(void);
 
 int kvm_vgic_inject_irq(struct kvm *kvm, struct kvm_vcpu *vcpu,
 			unsigned int intid, bool level, void *owner);
+void kvm_vgic_set_irq_ops(struct kvm_vcpu *vcpu, u32 vintid,
+			  struct irq_ops *ops);
+void kvm_vgic_clear_irq_ops(struct kvm_vcpu *vcpu, u32 vintid);
 int kvm_vgic_map_phys_irq(struct kvm_vcpu *vcpu, unsigned int host_irq,
-			  u32 vintid, struct irq_ops *ops);
+			  u32 vintid);
 int kvm_vgic_unmap_phys_irq(struct kvm_vcpu *vcpu, unsigned int vintid);
 int kvm_vgic_get_map(struct kvm_vcpu *vcpu, unsigned int vintid);
 bool kvm_vgic_map_is_active(struct kvm_vcpu *vcpu, unsigned int vintid);