Index: sys/arm64/arm64/db_interface.c
===================================================================
--- sys/arm64/arm64/db_interface.c
+++ sys/arm64/arm64/db_interface.c
@@ -157,11 +157,11 @@
 		*dst++ = *data++;
 	}
 
-	dsb();
+	dsb(sy);
 	/* Clean D-cache and invalidate I-cache */
 	cpu_dcache_wb_range(addr, (vm_size_t)size);
 	cpu_icache_sync_range(addr, (vm_size_t)size);
-	dsb();
+	dsb(sy);
 	isb();
 
 	return (0);
Index: sys/arm64/arm64/vfp.c
===================================================================
--- sys/arm64/arm64/vfp.c
+++ sys/arm64/arm64/vfp.c
@@ -120,7 +120,7 @@
 		td->td_pcb->pcb_fpcr = fpcr;
 		td->td_pcb->pcb_fpsr = fpsr;
 
-		dsb();
+		dsb(sy);
 		vfp_disable();
 	}
 	critical_exit();
Index: sys/arm64/include/atomic.h
===================================================================
--- sys/arm64/include/atomic.h
+++ sys/arm64/include/atomic.h
@@ -29,13 +29,29 @@
 #ifndef	_MACHINE_ATOMIC_H_
 #define	_MACHINE_ATOMIC_H_
 
-#define	isb()  __asm __volatile("isb" : : : "memory")
-#define	dsb()  __asm __volatile("dsb sy" : : : "memory")
-#define	dmb()  __asm __volatile("dmb sy" : : : "memory")
+#define isb()  __asm __volatile("isb" : : : "memory")
 
-#define	mb()   dmb()
-#define	wmb()  dmb()
-#define	rmb()  dmb()
+/*
+ * Options for DMB and DSB:
+ *	oshld	Outer Shareable, load
+ *	oshst	Outer Shareable, store
+ *	osh	Outer Shareable, all
+ *	nshld	Non-shareable, load
+ *	nshst	Non-shareable, store
+ *	nsh	Non-shareable, all
+ *	ishld	Inner Shareable, load
+ *	ishst	Inner Shareable, store
+ *	ish	Inner Shareable, all
+ *	ld	Full system, load
+ *	st	Full system, store
+ *	sy	Full system, all
+ */
+#define dsb(opt)  __asm __volatile("dsb " __STRING(opt) : : : "memory")
+#define dmb(opt)  __asm __volatile("dmb " __STRING(opt) : : : "memory")
+
+#define mb()   dmb(sy)	/* Full system memory barrier all */
+#define wmb()  dmb(st)	/* Full system memory barrier store */
+#define rmb()  dmb(ld)	/* Full system memory barrier load */
 
 static __inline void
 atomic_add_32(volatile uint32_t *p, uint32_t val)