[Pkg-xen-devel] Bug#679533: Bug#679533: Traffic forwarding issue between Xen domU/dom0

[Hans van Kranenburg]

So...

After disabling hyperthreading in the server bios we can no longer 
reproduce the bug. This is a HP Proliant DL360 G7. We've not yet tried 
to consistently reproduce on other hardware we have, but all production 
hosting servers we run now are of these G7 type with Intel Xeon X5650 or 
X5675 cpu.

The last test Frank reported, starting >20 of vms and in a loop 
rebooting them consistently reproduced the broken behaviour on a random 
network interface of a random vm.

We're now at >150 reboot cycles of all test vm's on a single dom0 with 
HT disabled. When enabling HT this fails consistently between 10-50 vm 
reboots.

So this still looks like some race condition bug. It's reproducible 
while running with either openvswitch or linux bridge, so it's only 
related to the actual dom0/domU passthrough of network traffic.

We're still gonna try to upgrade the test dom0 to wheezy with xen 4.1 
and linux 3.2 and see what happens with HT enabled and disabled.

I'm very interested in feedback from Xen/Linux developers about this. 
Enabling HT with Xen 4.0 and Linux 2.6.32 on debian is not safe right 
now. Been there, done that. :-)

During the past months, it seemed we're the only ones affected by this 
bug. Or, no-one is starting, stopping and live migrating xen vms as much 
as we do?

Thanks,
Hans