diff --git a/sys/compat/linuxkpi/common/include/linux/io.h b/sys/compat/linuxkpi/common/include/linux/io.h
--- a/sys/compat/linuxkpi/common/include/linux/io.h
+++ b/sys/compat/linuxkpi/common/include/linux/io.h
@@ -349,6 +349,14 @@
 }
 #define	ioread32be(addr)	ioread32be(addr)
 
+#undef ioread64
+static inline uint64_t
+ioread64(const volatile void *addr)
+{
+	return (readq(addr));
+}
+#define	ioread64(addr)		ioread64(addr)
+
 #undef iowrite8
 static inline void
 iowrite8(uint8_t v, volatile void *addr)