+ /*
+ * pfn_valid() relies on RCU, and may call into the scheduler on exiting
+ * the critical section. However, this would result in recursion with
+ * KMSAN. Therefore, disable preemption here, and re-enable preemption
+ * below while suppressing reschedules to avoid recursion.
+ *
+ * Note, this sacrifices occasionally breaking scheduling guarantees.
+ * Although, a kernel compiled with KMSAN has already given up on any
+ * performance guarantees due to being heavily instrumented.
+ */
+ preempt_disable();
+ ret = pfn_valid(x >> PAGE_SHIFT);
+ preempt_enable_no_resched();
+
+ return ret;