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Re: [Qemu-devel] [PATCH] dataplane: endian fix in host notification


From: Cornelia Huck
Subject: Re: [Qemu-devel] [PATCH] dataplane: endian fix in host notification
Date: Thu, 25 Jun 2015 18:34:47 +0200

On Thu, 25 Jun 2015 17:26:21 +0200
Greg Kurz <address@hidden> wrote:

> This field comes either LE with virtio 1.0, either guest endian with legacy.
> It must only be accessed with an accessor that knows about the appropriate
> endianness.
> 
> Signed-off-by: Greg Kurz <address@hidden>
> ---
>  hw/virtio/dataplane/vring.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/hw/virtio/dataplane/vring.c b/hw/virtio/dataplane/vring.c
> index 3fa421b9d773..a93ee2d338d7 100644
> --- a/hw/virtio/dataplane/vring.c
> +++ b/hw/virtio/dataplane/vring.c
> @@ -117,7 +117,7 @@ void vring_disable_notification(VirtIODevice *vdev, Vring 
> *vring)
>  bool vring_enable_notification(VirtIODevice *vdev, Vring *vring)
>  {
>      if (virtio_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX)) {
> -        vring_avail_event(&vring->vr) = vring->vr.avail->idx;
> +        vring_avail_event(&vring->vr) = vring_get_avail_idx(vdev, vring);
>      } else {
>          vring_clear_used_flags(vdev, vring, VRING_USED_F_NO_NOTIFY);
>      }
> 
Hm... we should publish in the same endianness as the queue, shouldn't
we? IOW, this seems fine.

OTOH, this prompted me to check for other places where we touch
vring_avail_event and it seems to me that we need to convert
vring->last_avail_idx before we set it in vring_pop().

I might be confused, though :)




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