Index: sys/amd64/include/vm.h
===================================================================
--- sys/amd64/include/vm.h
+++ sys/amd64/include/vm.h
@@ -43,5 +43,8 @@
 #define	VM_MEMATTR_WEAK_UNCACHEABLE	((vm_memattr_t)PAT_UNCACHED)
 
 #define	VM_MEMATTR_DEFAULT		VM_MEMATTR_WRITE_BACK
+#ifdef _KERNEL
+#define	VM_MEMATTR_DEVICE		VM_MEMATTR_UNCACHEABLE
+#endif
 
 #endif /* !_MACHINE_VM_H_ */
Index: sys/i386/include/vm.h
===================================================================
--- sys/i386/include/vm.h
+++ sys/i386/include/vm.h
@@ -43,5 +43,8 @@
 #define	VM_MEMATTR_WEAK_UNCACHEABLE	((vm_memattr_t)PAT_UNCACHED)
 
 #define	VM_MEMATTR_DEFAULT		VM_MEMATTR_WRITE_BACK
+#ifdef _KERNEL
+#define	VM_MEMATTR_DEVICE		VM_MEMATTR_UNCACHEABLE
+#endif
 
 #endif /* !_MACHINE_VM_H_ */
Index: sys/kern/subr_bus.c
===================================================================
--- sys/kern/subr_bus.c
+++ sys/kern/subr_bus.c
@@ -3155,7 +3155,7 @@
 {
 	bzero(args, sz);
 	args->size = sz;
-	args->memattr = VM_MEMATTR_UNCACHEABLE;
+	args->memattr = VM_MEMATTR_DEVICE;
 }
 
 /**
Index: sys/mips/include/vm.h
===================================================================
--- sys/mips/include/vm.h
+++ sys/mips/include/vm.h
@@ -42,4 +42,8 @@
 #define	VM_MEMATTR_WRITE_COMBINING	((vm_memattr_t)MIPS_CCA_WC)
 #endif
 
+#ifdef _KERNEL
+#define	VM_MEMATTR_DEVICE		VM_MEMATTR_UNCACHEABLE
+#endif
+
 #endif /* !_MACHINE_VM_H_ */
Index: sys/powerpc/include/vm.h
===================================================================
--- sys/powerpc/include/vm.h
+++ sys/powerpc/include/vm.h
@@ -42,4 +42,8 @@
 #define	VM_MEMATTR_WRITE_THROUGH	0x10
 #define	VM_MEMATTR_PREFETCHABLE		0x20
 
+#ifdef _KERNEL
+#define	VM_MEMATTR_DEVICE		VM_MEMATTR_DEFAULT
+#endif
+
 #endif /* !_MACHINE_VM_H_ */