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

Cornelia Huck
2014-12-01T12:21:03Z

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 |