Index: head/sys/cddl/compat/opensolaris/sys/atomic.h
===================================================================
--- head/sys/cddl/compat/opensolaris/sys/atomic.h
+++ head/sys/cddl/compat/opensolaris/sys/atomic.h
@@ -51,7 +51,7 @@
 extern void membar_producer(void);
 
 #if defined(__sparc64__) || defined(__powerpc__) || defined(__arm__) || \
-    defined(__mips__)
+    defined(__mips__) || defined(__aarch64__)
 extern void atomic_or_8(volatile uint8_t *target, uint8_t value);
 #else
 static __inline void
Index: head/sys/cddl/contrib/opensolaris/uts/common/sys/isa_defs.h
===================================================================
--- head/sys/cddl/contrib/opensolaris/uts/common/sys/isa_defs.h
+++ head/sys/cddl/contrib/opensolaris/uts/common/sys/isa_defs.h
@@ -346,6 +346,48 @@
 #define	_DONT_USE_1275_GENERIC_NAMES
 #define	_HAVE_CPUID_INSN
 
+#elif defined(__aarch64__)
+
+/*
+ * Define the appropriate "processor characteristics"
+ */
+#define	_STACK_GROWS_DOWNWARD
+#define	_LONG_LONG_LTOH
+#define	_BIT_FIELDS_LTOH
+#define	_IEEE_754
+#define	_CHAR_IS_UNSIGNED
+#define	_BOOL_ALIGNMENT			1
+#define	_CHAR_ALIGNMENT			1
+#define	_SHORT_ALIGNMENT		2
+#define	_INT_ALIGNMENT			4
+#define	_FLOAT_ALIGNMENT		4
+#define	_FLOAT_COMPLEX_ALIGNMENT	4
+#define	_LONG_ALIGNMENT			8
+#define	_LONG_LONG_ALIGNMENT		8
+#define	_DOUBLE_ALIGNMENT		8
+#define	_DOUBLE_COMPLEX_ALIGNMENT	8
+#define	_LONG_DOUBLE_ALIGNMENT		16
+#define	_LONG_DOUBLE_COMPLEX_ALIGNMENT	16
+#define	_POINTER_ALIGNMENT		8
+#define	_MAX_ALIGNMENT			16
+#define	_ALIGNMENT_REQUIRED		1
+
+#define	_LONG_LONG_ALIGNMENT_32		_LONG_LONG_ALIGNMENT
+
+/*
+ * Define the appropriate "implementation choices"
+ */
+#if !defined(_LP64)
+#define	_LP64
+#endif
+#define	_SUNOS_VTOC_16
+#define	_DMA_USES_PHYSADDR
+#define	_FIRMWARE_NEEDS_FDISK
+#define	_PSM_MODULES
+#define	_RTC_CONFIG
+#define	_DONT_USE_1275_GENERIC_NAMES
+#define	_HAVE_CPUID_INSN
+
 #elif defined(__arm__)
 
 /*