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From: Laurent Vivier <lvivier@redhat.com>
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Date: Thu, 7 Jan 2016 21:07:26 +0100
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Subject: Re: [Qemu-devel] [PATCH 5/6] vhost: move virtio 1.0 check to
 cross-endian helper
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To: Greg Kurz <gkurz@linux.vnet.ibm.com>, "Michael S. Tsirkin" <mst@redhat.com>
Cc: qemu-devel@nongnu.org



On 07/01/2016 12:32, Greg Kurz wrote:
> Indeed vhost doesn't need to ask for vring endian fixing if the device is
> virtio 1.0, since it is already handled by the in-kernel vhost driver. This
> patch simply consolidates the logic into the existing helper.
> 
> Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
> Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
> ---
>  hw/virtio/vhost.c |    9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
> index 2e1e792d599e..aef750df22ad 100644
> --- a/hw/virtio/vhost.c
> +++ b/hw/virtio/vhost.c
> @@ -750,6 +750,9 @@ static void vhost_log_stop(MemoryListener *listener,
>  
>  static inline bool vhost_needs_vring_endian(VirtIODevice *vdev)
>  {
> +    if (virtio_vdev_has_feature(vdev, VIRTIO_F_VERSION_1)) {
> +        return false;
> +    }
>  #ifdef TARGET_IS_BIENDIAN
>  #ifdef HOST_WORDS_BIGENDIAN
>      return !virtio_is_big_endian(vdev);
> @@ -811,8 +814,7 @@ static int vhost_virtqueue_start(struct vhost_dev *dev,
>          return -errno;
>      }
>  
> -    if (!virtio_vdev_has_feature(vdev, VIRTIO_F_VERSION_1) &&
> -        vhost_needs_vring_endian(vdev)) {
> +    if (vhost_needs_vring_endian(vdev)) {
>          r = vhost_virtqueue_set_vring_endian_legacy(dev,
>                                                      virtio_is_big_endian(vdev),
>                                                      vhost_vq_index);
> @@ -908,8 +910,7 @@ static void vhost_virtqueue_stop(struct vhost_dev *dev,
>      /* In the cross-endian case, we need to reset the vring endianness to
>       * native as legacy devices expect so by default.
>       */
> -    if (!virtio_vdev_has_feature(vdev, VIRTIO_F_VERSION_1) &&
> -        vhost_needs_vring_endian(vdev)) {
> +    if (vhost_needs_vring_endian(vdev)) {
>          r = vhost_virtqueue_set_vring_endian_legacy(dev,
>                                                      !virtio_is_big_endian(vdev),
>                                                      vhost_vq_index);
> 
> 

IMHO, I think 4/6 and 5/6 can be merged as there is no change in the
behavior and they are only consolidating code.