[PATCH v4 24/49] KVM: arm64: Invert ap_list sorting to push active interrupts out

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

Having established that pending interrupts should have priority
to be moved into the LRs over the active interrupts, implement this
in the ap_list sorting.

Tested-by: Fuad Tabba <tabba@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
---
arch/arm64/kvm/vgic/vgic.c | 27 ++++++++++++---------------
1 file changed, 12 insertions(+), 15 deletions(-)

diff --git a/arch/arm64/kvm/vgic/vgic.c b/arch/arm64/kvm/vgic/vgic.c
index 004010104659a..c7a5454ac4c9f 100644
--- a/arch/arm64/kvm/vgic/vgic.c
+++ b/arch/arm64/kvm/vgic/vgic.c
@@ -270,10 +270,7 @@ struct kvm_vcpu *vgic_target_oracle(struct vgic_irq *irq)
* well, the first items in the list being the first things populated in the
* LRs.
*
- * A hard rule is that active interrupts can never be pushed out of the LRs
- * (and therefore take priority) since we cannot reliably trap on deactivation
- * of IRQs and therefore they have to be present in the LRs.
- *
+ * 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.
*
@@ -298,21 +295,21 @@ 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);

- if (irqa->active || irqb->active) {
- ret = (int)irqb->active - (int)irqa->active;
- goto out;
- }
+ penda = irqa->enabled && irq_is_pending(irqa) && !irqa->active;
+ pendb = irqb->enabled && irq_is_pending(irqb) && !irqb->active;

- penda = irqa->enabled && irq_is_pending(irqa);
- pendb = irqb->enabled && irq_is_pending(irqb);
+ ret = (int)pendb - (int)penda;
+ if (ret)
+ goto out;

- if (!penda || !pendb) {
- ret = (int)pendb - (int)penda;
+ /* Both pending and enabled, sort by priority (lower number first) */
+ ret = (int)irqa->priority - (int)irqb->priority;
+ if (ret)
goto out;
- }

- /* Both pending and enabled, sort by priority */
- ret = irqa->priority - irqb->priority;
+ /* Finally, HW bit active interrupts have priority over non-HW ones */
+ ret = (int)irqb->hw - (int)irqa->hw;
+
out:
raw_spin_unlock(&irqb->irq_lock);
raw_spin_unlock(&irqa->irq_lock);
--
2.47.3