arm64: KVM: vgic-v3: Do not save an LR known to be empty

On exit, any empty LR will be signaled in ICH_ELRSR_EL2. Which
means that we do not have to save it, and we can just clear
its state in the in-memory copy.
Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

arch/arm64/kvm/hyp/vgic-v3-sr.c

@@ -187,8 +187,15 @@ void __hyp_text __vgic_v3_save_state(struct kvm_vcpu *vcpu)
 		save_maint_int_state(vcpu, max_lr_idx + 1);
 
 		for (i = 0; i <= max_lr_idx; i++) {
-			if (vcpu->arch.vgic_cpu.live_lrs & (1UL << i))
-				cpu_if->vgic_lr[i] = __gic_v3_get_lr(i);
+			if (!(vcpu->arch.vgic_cpu.live_lrs & (1UL << i)))
+				continue;
+
+			if (cpu_if->vgic_elrsr & (1 << i)) {
+				cpu_if->vgic_lr[i] &= ~ICH_LR_STATE;
+				continue;
+			}
+
+			cpu_if->vgic_lr[i] = __gic_v3_get_lr(i);
 		}
 
 		switch (nr_pri_bits) {