[PULL 20/79] KVM: arm/arm64: vgic: Only set underflow when actually out of LRs

[Christoffer Dall]

We currently assume that all the interrupts in our AP list will be
queued to LRs, but that's not necessarily the case, because some of them
could have been migrated away to different VCPUs and only the VCPU
thread itself can remove interrupts from its AP list.

Therefore, slightly change the logic to only setting the underflow
interrupt when we actually run out of LRs.

As it turns out, this allows us to further simplify the handling in
vgic_sync_hwstate in later patches.

Acked-by: Marc Zyngier <marc.zyngier at arm.com>
Signed-off-by: Christoffer Dall <cdall at linaro.org>
---
 virt/kvm/arm/vgic/vgic.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/virt/kvm/arm/vgic/vgic.c b/virt/kvm/arm/vgic/vgic.c
index 1043291..442f7df 100644
--- a/virt/kvm/arm/vgic/vgic.c
+++ b/virt/kvm/arm/vgic/vgic.c
@@ -601,10 +601,8 @@ static void vgic_flush_lr_state(struct kvm_vcpu *vcpu)
 
 	DEBUG_SPINLOCK_BUG_ON(!spin_is_locked(&vgic_cpu->ap_list_lock));
 
-	if (compute_ap_list_depth(vcpu) > kvm_vgic_global_state.nr_lr) {
-		vgic_set_underflow(vcpu);
+	if (compute_ap_list_depth(vcpu) > kvm_vgic_global_state.nr_lr)
 		vgic_sort_ap_list(vcpu);
-	}
 
 	list_for_each_entry(irq, &vgic_cpu->ap_list_head, ap_list) {
 		spin_lock(&irq->irq_lock);
@@ -623,8 +621,12 @@ static void vgic_flush_lr_state(struct kvm_vcpu *vcpu)
 next:
 		spin_unlock(&irq->irq_lock);
 
-		if (count == kvm_vgic_global_state.nr_lr)
+		if (count == kvm_vgic_global_state.nr_lr) {
+			if (!list_is_last(&irq->ap_list,
+					  &vgic_cpu->ap_list_head))
+				vgic_set_underflow(vcpu);
 			break;
+		}
 	}
 
 	vcpu->arch.vgic_cpu.used_lrs = count;
-- 
2.9.0