# \[PATCH 3/3\] tools/virtio: use {READ,WRITE}\_ONCE() in uaccess.h

- From: Mark Rutland \<mark.rutland@arm.com\>
- Date: 2016-11-24 10:25:45 
- List: netdev
- Page: https://ratatoskr.run/netdev/2016/11/4882171
- Thread: https://ratatoskr.run/kvm/2016/11/4882170/t.md

```text
As a step towards killing off ACCESS_ONCE, use {READ,WRITE}_ONCE() for the
virtio tools uaccess primitives, pulling these in from <linux/compiler.h>.

With this done, we can kill off the now-unused ACCESS_ONCE() definition.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Jason Wang <redacted>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: <redacted>
Cc: <redacted>
---
 tools/virtio/linux/uaccess.h | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/tools/virtio/linux/uaccess.h b/tools/virtio/linux/uaccess.h
index 0a578fe..fa05d01 100644
--- a/tools/virtio/linux/uaccess.h
+++ b/tools/virtio/linux/uaccess.h
@@ -1,8 +1,9 @@
 #ifndef UACCESS_H
 #define UACCESS_H
-extern void *__user_addr_min, *__user_addr_max;
 
-#define ACCESS_ONCE(x) (*(volatile typeof(x) *)&(x))
+#include <linux/compiler.h>
+
+extern void *__user_addr_min, *__user_addr_max;
 
 static inline void __chk_user_ptr(const volatile void *p, size_t size)
 {
@@ -13,7 +14,7 @@ static inline void __chk_user_ptr(const volatile void *p, size_t size)
 ({								\
 	typeof(ptr) __pu_ptr = (ptr);				\
 	__chk_user_ptr(__pu_ptr, sizeof(*__pu_ptr));		\
-	ACCESS_ONCE(*(__pu_ptr)) = x;				\
+	WRITE_ONCE(*(__pu_ptr), x);				\
 	0;							\
 })
 
@@ -21,7 +22,7 @@ static inline void __chk_user_ptr(const volatile void *p, size_t size)
 ({								\
 	typeof(ptr) __pu_ptr = (ptr);				\
 	__chk_user_ptr(__pu_ptr, sizeof(*__pu_ptr));		\
-	x = ACCESS_ONCE(*(__pu_ptr));				\
+	x = READ_ONCE(*(__pu_ptr));				\
 	0;							\
 })
 
-- 
2.7.4

```