netdev - Re: [PATCH 3/3] tools/virtio: use {READ,WRITE}

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Date:   Fri, 25 Nov 2016 10:40:48 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Mark Rutland <mark.rutland@....com>, linux-kernel@...r.kernel.org
Cc:     dave@...olabs.net, dbueso@...e.de, dvyukov@...gle.com,
        kvm@...r.kernel.org, mst@...hat.com, netdev@...r.kernel.org,
        paulmck@...ux.vnet.ibm.com,
        virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH 3/3] tools/virtio: use {READ,WRITE}_ONCE() in uaccess.h



On 2016年11月24日 18:25, Mark Rutland wrote:
> 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@....com>
> Cc: Jason Wang <jasowang@...hat.com>
> Cc: Michael S. Tsirkin <mst@...hat.com>
> Cc: linux-kernel@...r.kernel.org
> Cc: virtualization@...ts.linux-foundation.org
> ---
>   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;							\
>   })
>   

Reviewed-by: Jason Wang <jasowang@...hat.com>