There are times when the default behaviour of vgic_queue_irq_unlock()
is undesirable. This is because some GICs, such a GICv5 which is the
main driver for this change, handle the majority of the interrupt
lifecycle in hardware. In this case, there is no need for a per-VCPU
AP list as the interrupt can be made pending directly. This is done
either via the ICH_PPI_x_EL2 registers for PPIs, or with the VDPEND
system instruction for SPIs and LPIs.

The vgic_queue_irq_unlock() function is made overridable using a new
function pointer in struct irq_ops. vgic_queue_irq_unlock() is
overridden if the function pointer is non-null.

This new irq_op is unused in this change - it is purely providing the
infrastructure itself. The subsequent PPI injection changes provide a
demonstration of the usage of the queue_irq_unlock irq_op.

Signed-off-by: Sascha Bischoff <redacted>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
---
 arch/arm64/kvm/vgic/vgic.c | 3 +++
 include/kvm/arm_vgic.h     | 9 +++++++++
 2 files changed, 12 insertions(+)

diff --git a/arch/arm64/kvm/vgic/vgic.c b/arch/arm64/kvm/vgic/vgic.c
index 62e58fdf611d3..49d65e8cc742b 100644
--- a/arch/arm64/kvm/vgic/vgic.c
+++ b/arch/arm64/kvm/vgic/vgic.c

@@ -404,6 +404,9 @@ bool vgic_queue_irq_unlock(struct kvm *kvm, struct vgic_irq *irq,
 
 	lockdep_assert_held(&irq->irq_lock);
 
+	if (irq->ops && irq->ops->queue_irq_unlock)
+		return irq->ops->queue_irq_unlock(kvm, irq, flags);
+
 retry:
 	vcpu = vgic_target_oracle(irq);
 	if (irq->vcpu || !vcpu) {

diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
index a4416afca5efc..f469ecea959ba 100644
--- a/include/kvm/arm_vgic.h
+++ b/include/kvm/arm_vgic.h

@@ -173,6 +173,8 @@ enum vgic_irq_config {
 	VGIC_CONFIG_LEVEL
 };
 
+struct vgic_irq;
+
 /*
  * Per-irq ops overriding some common behavious.
  *

@@ -191,6 +193,13 @@ struct irq_ops {
 	 * peaking into the physical GIC.
 	 */
 	bool (*get_input_level)(int vintid);
+
+	/*
+	 * Function pointer to override the queuing of an IRQ.
+	 */
+	bool (*queue_irq_unlock)(struct kvm *kvm, struct vgic_irq *irq,
+				unsigned long flags) __releases(&irq->irq_lock);
+
 };
 
 struct vgic_irq {

-- 
2.34.1