>> As the concerned user, what does this mean to me?  It will only affect
>> SMP systems?  It is a bug in Xen or netfilter?
> 
> Probably a Xen bug, but if so then it's basically a memory corruption.

Might also be a netfilter bug which is simply triggered by the way how
xen manages the memory.  Due to ballooning you can have holes in memory,
so out-of-range access may fault with xen whereas it will go unnoticed
with normal kernels.

One such beast is in bridging netfilter code, additionally it triggers
with certain ethernet cards only, patch below.  Pinned down last week ;)

cheers,

  Gerd