Re: [Qemu-devel] [PATCH] virtio-net: unbreak self announcement and guest offloads after migration

[Greg Kurz <gkurz@linux.vnet.ibm.com>]

On Fri, 11 Sep 2015 16:01:56 +0800
Jason Wang <jasowang@redhat.com> wrote:

> After commit 019a3edbb25f1571e876f8af1ce4c55412939e5d ("virtio: make
> features 64bit wide"). Device's guest_features was actually set after
> vdc->load(). This breaks the assumption that device specific load()

Yeah... subsections are loaded after the device specific state...

> function can check guest_features. For virtio-net, self announcement
> and guest offloads won't work after migration.
> 
> Fixing this by defer them to virtio_net_load() where guest_features
> were guaranteed to be set. Other virtio devices looks fine.
> 
> Fixes: 019a3edbb25f1571e876f8af1ce4c55412939e5d
>        ("virtio: make features 64bit wide")
> Cc: qemu-stable@nongnu.org
> Cc: Gerd Hoffmann <kraxel@redhat.com>
> Signed-off-by: Jason Wang <jasowang@redhat.com>
> ---

Reviewed-by: Greg Kurz <gkurz@linux.vnet.ibm.com>

>  hw/net/virtio-net.c | 40 +++++++++++++++++++++++-----------------
>  1 file changed, 23 insertions(+), 17 deletions(-)
> 
> diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
> index f72eebf..2775e6a 100644
> --- a/hw/net/virtio-net.c
> +++ b/hw/net/virtio-net.c
> @@ -1458,11 +1458,33 @@ static int virtio_net_load(QEMUFile *f, void *opaque, int version_id)
>  {
>      VirtIONet *n = opaque;
>      VirtIODevice *vdev = VIRTIO_DEVICE(n);
> +    int ret;
> 
>      if (version_id < 2 || version_id > VIRTIO_NET_VM_VERSION)
>          return -EINVAL;
> 
> -    return virtio_load(vdev, f, version_id);
> +    ret = virtio_load(vdev, f, version_id);
> +    if (ret) {
> +        return ret;
> +    }
> +
> +    if (virtio_vdev_has_feature(vdev, VIRTIO_NET_F_CTRL_GUEST_OFFLOADS)) {
> +        n->curr_guest_offloads = qemu_get_be64(f);
> +    } else {
> +        n->curr_guest_offloads = virtio_net_supported_guest_offloads(n);
> +    }
> +
> +    if (peer_has_vnet_hdr(n)) {
> +        virtio_net_apply_guest_offloads(n);
> +    }
> +
> +    if (virtio_vdev_has_feature(vdev, VIRTIO_NET_F_GUEST_ANNOUNCE) &&
> +        virtio_vdev_has_feature(vdev, VIRTIO_NET_F_CTRL_VQ)) {
> +        n->announce_counter = SELF_ANNOUNCE_ROUNDS;
> +        timer_mod(n->announce_timer, qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL));
> +    }
> +
> +    return 0;
>  }
> 
>  static int virtio_net_load_device(VirtIODevice *vdev, QEMUFile *f,
> @@ -1559,16 +1581,6 @@ static int virtio_net_load_device(VirtIODevice *vdev, QEMUFile *f,
>          }
>      }
> 
> -    if (virtio_vdev_has_feature(vdev, VIRTIO_NET_F_CTRL_GUEST_OFFLOADS)) {
> -        n->curr_guest_offloads = qemu_get_be64(f);
> -    } else {
> -        n->curr_guest_offloads = virtio_net_supported_guest_offloads(n);
> -    }
> -
> -    if (peer_has_vnet_hdr(n)) {
> -        virtio_net_apply_guest_offloads(n);
> -    }
> -
>      virtio_net_set_queues(n);
> 
>      /* Find the first multicast entry in the saved MAC filter */
> @@ -1586,12 +1598,6 @@ static int virtio_net_load_device(VirtIODevice *vdev, QEMUFile *f,
>          qemu_get_subqueue(n->nic, i)->link_down = link_down;
>      }
> 
> -    if (virtio_vdev_has_feature(vdev, VIRTIO_NET_F_GUEST_ANNOUNCE) &&
> -        virtio_vdev_has_feature(vdev, VIRTIO_NET_F_CTRL_VQ)) {
> -        n->announce_counter = SELF_ANNOUNCE_ROUNDS;
> -        timer_mod(n->announce_timer, qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL));
> -    }
> -
>      return 0;
>  }
>