Re: [PATCH v7 30/46] vhost/net: force len for TX to host endian

[Cornelia Huck <cornelia.huck@de.ibm.com>]

On Sun, 30 Nov 2014 17:11:44 +0200
"Michael S. Tsirkin" <mst@redhat.com> wrote:

> vhost/net keeps a copy of some used ring but (ab)uses length
> field for internal house-keeping. This works because
> for tx used length is always 0.
> Suppress sparse errors: we use native endian-ness internally but never
> expose it to guest.

I admit that I find this patch description hard to read :)


"vhost/net keeps a copy of the used ring in host memory but (ab)uses
the length field for internal house-keeping. This works because the
length in the used ring for tx is always 0. In order to suppress sparse
errors, we need to force native endianness."

?

> 
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> Reviewed-by: Jason Wang <jasowang@redhat.com>
> ---
>  drivers/vhost/net.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
> index 8dae2f7..dce5c58 100644
> --- a/drivers/vhost/net.c
> +++ b/drivers/vhost/net.c
> @@ -48,15 +48,15 @@ MODULE_PARM_DESC(experimental_zcopytx, "Enable Zero Copy TX;"
>   * status internally; used for zerocopy tx only.
>   */
>  /* Lower device DMA failed */
> -#define VHOST_DMA_FAILED_LEN	3
> +#define VHOST_DMA_FAILED_LEN	((__force __virtio32)3)
>  /* Lower device DMA done */
> -#define VHOST_DMA_DONE_LEN	2
> +#define VHOST_DMA_DONE_LEN	((__force __virtio32)2)
>  /* Lower device DMA in progress */
> -#define VHOST_DMA_IN_PROGRESS	1
> +#define VHOST_DMA_IN_PROGRESS	((__force __virtio32)1)
>  /* Buffer unused */
> -#define VHOST_DMA_CLEAR_LEN	0
> +#define VHOST_DMA_CLEAR_LEN	((__force __virtio32)0)
> 
> -#define VHOST_DMA_IS_DONE(len) ((len) >= VHOST_DMA_DONE_LEN)
> +#define VHOST_DMA_IS_DONE(len) ((__force u32)(len) >= (__force u32)VHOST_DMA_DONE_LEN)
> 
>  enum {
>  	VHOST_NET_FEATURES = VHOST_FEATURES |