kvm nfs hang
I ran into a strange NFS + KVM issue. Every so often under heavy NFS load my KVM client would hang retrying the nfs server. On the console the client was showing:
nfs: server host not responding, still trying
I found this bug post which does not seem to have been resolved in 2.6.24.
Using the kvm flag -net nic,model=rtl8139
fixed the problem for me.