[Qemu-devel] qemu-kvm-0.11 regression, crashes on older guests with virtio network

[Dustin Kirkland]

I believe that we have identified a regression in qemu-kvm-0.11.0.

The kvm process crashes for older guests with virtio networking, when
the guest's incoming network connection is saturated.  The subject
guest is Ubuntu 8.04 Hardy, 2.6.24 kernel with virtio backports.

For your convenience, I have uploaded a stock, ~260MB Ubuntu 8.04 disk
image (user/pw = ubuntu) that I'm using to reproduce the problem at:
 * http://rookery.canonical.com/~kirkland/hardy.img.bz2

The command line is:
 * sudo /usr/bin/kvm -m 512 -net nic,model=virtio -net
tap,script=/home/kirkland/bin/bridge.sh -drive
file=hardy.img,if=virtio,index=0,boot=on

The bridge script is:
 * http://rookery.canonical.com/~kirkland/bridge.sh

I'm saturating the guest's incoming network connection, with:
  address@hidden nc -lp 1234 > /dev/null
and
  address@hidden cat /dev/urandom | nc -w 3 guest_ip 1234

In less than a second of sending, the vm crashes with:
  virtio-net truncating packet

I have strace logs, if that's helpful.

I have not reproduced the problem:
 a) by saturating the guest's outgoing network
 b) with newer guests ( >= 2.6.27 )
 c) on kvm-84 on the host

We're tracking this issue at:
 * https://bugs.launchpad.net/ubuntu/+source/qemu-kvm/+bug/458521

I'll gladly review and test patches, or take pointers on where I might
look to solve this issue.

-- 
:-Dustin