[PATCH v4 25/49] KVM: arm64: Move undeliverable interrupts to the end of ap_list

Marc Zyngier
2025-11-20T17:26:01Z

Interrupts in the ap_list that cannot be acted upon because they
are not enabled, or that their group is not enabled, shouldn't
make it into the LRs if we are space-constrained.

Tested-by: Fuad Tabba <tabba@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
---
arch/arm64/kvm/vgic/vgic.c | 23 ++++++++++++++++++++++-
1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kvm/vgic/vgic.c b/arch/arm64/kvm/vgic/vgic.c
index c7a5454ac4c9f..abe01c9c6b364 100644
--- a/arch/arm64/kvm/vgic/vgic.c
+++ b/arch/arm64/kvm/vgic/vgic.c
@@ -265,6 +265,11 @@ struct kvm_vcpu *vgic_target_oracle(struct vgic_irq *irq)
return NULL;
}

+struct vgic_sort_info {
+ struct kvm_vcpu *vcpu;
+ struct vgic_vmcr vmcr;
+};
+
/*
* The order of items in the ap_lists defines how we'll pack things in LRs as
* well, the first items in the list being the first things populated in the
@@ -273,6 +278,7 @@ struct kvm_vcpu *vgic_target_oracle(struct vgic_irq *irq)
* Pending, non-active interrupts must be placed at the head of the list.
* Otherwise things should be sorted by the priority field and the GIC
* hardware support will take care of preemption of priority groups etc.
+ * Interrupts that are not deliverable should be at the end of the list.
*
* Return negative if "a" sorts before "b", 0 to preserve order, and positive
* to sort "b" before "a".
@@ -282,6 +288,8 @@ static int vgic_irq_cmp(void *priv, const struct list_head *a,
{
struct vgic_irq *irqa = container_of(a, struct vgic_irq, ap_list);
struct vgic_irq *irqb = container_of(b, struct vgic_irq, ap_list);
+ struct vgic_sort_info *info = priv;
+ struct kvm_vcpu *vcpu = info->vcpu;
bool penda, pendb;
int ret;

@@ -295,6 +303,17 @@ static int vgic_irq_cmp(void *priv, const struct list_head *a,
raw_spin_lock(&irqa->irq_lock);
raw_spin_lock_nested(&irqb->irq_lock, SINGLE_DEPTH_NESTING);

+ /* Undeliverable interrupts should be last */
+ ret = (int)(vgic_target_oracle(irqb) == vcpu) - (int)(vgic_target_oracle(irqa) == vcpu);
+ if (ret)
+ goto out;
+
+ /* Same thing for interrupts targeting a disabled group */
+ ret = (int)(irqb->group ? info->vmcr.grpen1 : info->vmcr.grpen0);
+ ret -= (int)(irqa->group ? info->vmcr.grpen1 : info->vmcr.grpen0);
+ if (ret)
+ goto out;
+
penda = irqa->enabled && irq_is_pending(irqa) && !irqa->active;
pendb = irqb->enabled && irq_is_pending(irqb) && !irqb->active;

@@ -320,10 +339,12 @@ static int vgic_irq_cmp(void *priv, const struct list_head *a,
static void vgic_sort_ap_list(struct kvm_vcpu *vcpu)
{
struct vgic_cpu *vgic_cpu = &vcpu->arch.vgic_cpu;
+ struct vgic_sort_info info = { .vcpu = vcpu, };

lockdep_assert_held(&vgic_cpu->ap_list_lock);

- list_sort(NULL, &vgic_cpu->ap_list_head, vgic_irq_cmp);
+ vgic_get_vmcr(vcpu, &info.vmcr);
+ list_sort(&info, &vgic_cpu->ap_list_head, vgic_irq_cmp);
}

/*
--
2.47.3