[ovs-dev] Kernel BUG on Xen

Nick Couchman Nick.Couchman at seakr.com
Mon Apr 26 17:16:31 UTC 2010

> Can you try applying this patch to see if it makes a difference?
> diff --git a/datapath/datapath.c b/datapath/datapath.c
> index e1320f2..fe90829 100644
> --- a/datapath/datapath.c
> +++ b/datapath/datapath.c
> @@ -554,6 +554,8 @@ static int skb_pull_up_to(struct sk_buff *skb, void
> *ptr)
>  {
>   if (ptr < (void *)skb->tail)
>   return 1;
> + if (ptr - (void *)skb->data > skb->len)
> + return 0;
>   if (__pskb_pull_tail(skb,
>       ptr - (void *)skb->data - skb_headlen(skb))) {
>   return 1;

As reported before, no change with this patch.  I've also been in touch with James Harper, the developer of the Windows GPL PV drivers I'm using.  He suggested trying to leave checksum offloading enabled but disable Large Send Offload and Scatter/Gather.  I tried that, with the same result - kernel BUG.

One other interesting thing that I found...I'm using Open vSwitch with a primary bridge that has tagged VLANs, then creating "fake bridges" that translate those into untagged VLANs that the system can use.  When the domU interface is connected to the primary bridge that has tagged VLANs, there is no crash.  Of course, there's not really any usable traffic - just the guest sending out DHCP requests and looking for responses, but seeing tagged VLAN traffic.  The crash only occurs when the interface for the Xen domU is on one of the untagged fake bridges.  Don't know if that helps any or not, but thought I'd throw it out there.


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