arm64: KVM: vgic-v3: Only wipe LRs on vcpu exit

So far, we're always writing all possible LRs, setting the empty
ones with a zero value. This is obvious doing a low of work for
nothing, and we're better off clearing those we've actually
dirtied on the exit path (it is very rare to inject more than one
interrupt at a time anyway).
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

@@ -196,6 +196,7 @@ void __hyp_text __vgic_v3_save_state(struct kvm_vcpu *vcpu)
 			}
 
 			cpu_if->vgic_lr[i] = __gic_v3_get_lr(i);
+			__gic_v3_set_lr(0, i);
 		}
 
 		switch (nr_pri_bits) {
@@ -293,12 +294,10 @@ void __hyp_text __vgic_v3_restore_state(struct kvm_vcpu *vcpu)
 		}
 
 		for (i = 0; i <= max_lr_idx; i++) {
-			val = 0;
-
-			if (live_lrs & (1 << i))
-				val = cpu_if->vgic_lr[i];
+			if (!(live_lrs & (1 << i)))
+				continue;
 
-			__gic_v3_set_lr(val, i);
+			__gic_v3_set_lr(cpu_if->vgic_lr[i], i);
 		}
 	}