diff --git a/inc/hf/cpu.h b/inc/hf/cpu.h
index d2029dd..76d71d6 100644
--- a/inc/hf/cpu.h
+++ b/inc/hf/cpu.h
@@ -78,6 +78,7 @@
 	 */
 	uint32_t irq_disable_count;
 
+	/** See api.c for the partial ordering on locks. */
 	struct spinlock lock;
 
 	/** Determines whether or not the cpu is currently on. */
diff --git a/inc/hf/vm.h b/inc/hf/vm.h
index dfe80b9..69ceac7 100644
--- a/inc/hf/vm.h
+++ b/inc/hf/vm.h
@@ -41,6 +41,7 @@
 
 struct vm {
 	uint32_t id;
+	/** See api.c for the partial ordering on locks. */
 	struct spinlock lock;
 	uint32_t vcpu_count;
 	struct vcpu vcpus[MAX_CPUS];