domU to domU networking issues in v3.7? (netserver/netperf failing to communicate)

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

Hey Ian, Xen-devel mailingl list,

I think the issue of 70% traffic lost was actually introduced in v3.6 or
perhaps v3.5. Annie and Marcos (CC-ed here) are looking to see which of
the releases introduced this. The issue we are seeing is that a domU
to domU communication breaks - this is with netperf/netserver talking to
each other.

Anyhow, I think the 3.7 compound page exacerbated the problem and also
(at least on some of my test hardware) exposed existing issues with
drivers. The issue I have is that the 'skge' driver has a bug that has
been there for ages (I tested way back to 3.0 and still saw it) were it
can not work with SWIOTLB. It is probably missing an pci_dma_sync
somewhere. 

Anyhow the compound page got me to look at Xen-SWIOTLB and that looks
OK. Even with synthetic driver (the fake one I posted somewhere) it
dealt with compound pages properly (with debug or non-debug Xen
hypervisor).

So was wondering if you had looked at this in more details? Any
ideas? Or would it be more prudent to ask that once we know for sure
which Linux release introduced the communication failures between
guests?