Re: [Qemu-devel] [PATCH 01/15] s390x: fix virtio feature bitmap

[Aurelien Jarno]

On Mon, Apr 04, 2011 at 04:32:10PM +0200, Alexander Graf wrote:
> The feature bitmap in the s390 virtio machine is little endian. To
> address for that, we need to bswap the values after reading them out.
> 
> Signed-off-by: Alexander Graf <address@hidden>
> ---
>  hw/s390-virtio-bus.c |    4 ++--
>  1 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/s390-virtio-bus.c b/hw/s390-virtio-bus.c
> index 58af164..60e0135 100644
> --- a/hw/s390-virtio-bus.c
> +++ b/hw/s390-virtio-bus.c
> @@ -223,7 +223,7 @@ void s390_virtio_device_sync(VirtIOS390Device *dev)
>      cur_offs += num_vq * VIRTIO_VQCONFIG_LEN;
>  
>      /* Sync feature bitmap */
> -    stl_phys(cur_offs, dev->host_features);
> +    stl_phys(cur_offs, bswap32(dev->host_features));

Is bswap32 correct here for both big and little endian guests? I don't
really understand the reason why a bswap is needed here, especially
given that AFAIK this code was already used when using KVM.
  
>      dev->feat_offs = cur_offs + dev->feat_len;
>      cur_offs += dev->feat_len * 2;
> @@ -246,7 +246,7 @@ void s390_virtio_device_update_status(VirtIOS390Device 
> *dev)
>  
>      /* Update guest supported feature bitmap */
>  
> -    features = ldl_phys(dev->feat_offs);
> +    features = bswap32(ldl_phys(dev->feat_offs));
>      if (vdev->set_features) {
>          vdev->set_features(vdev, features);
>      }
> -- 
> 1.6.0.2
> 
> 
> 

-- 
Aurelien Jarno                          GPG: 1024D/F1BCDB73
address@hidden                 http://www.aurel32.net