Guest Hang Bugs

[James Thomason <james@divide.org>]

Hello, 

I am able to reliably reproduce a condition where a guest goes into a tight
loop or spinlock on all running cores.  The scenario is exactly as described
in bug 2351676, though my environment differs as detailed below.  My
observation is that the issue is correlated to the number of VCPUs assigned
to the guest and CPU load. The higher the number of VCPUs and CPU
utilization, the more easily it is triggered.  If a KVM developer is
interested in debugging live, I might be able to arrange getting the system
in question into a DMZ.  A review of the kvm tracker leads me to believe
that the following bugs are possibly related:

[ 2351676 ] Guests hang periodically on Ubuntu-8.10
[ 2353811 ] Solaris 10 guest unstable
[ 2494730 ] Guests "stalling" on kvm-82
[ 2138079 ] kvm locks up system
[ 2113643 ] guests AND host still getting stuck under CPU load

KVM Host Configuration:

4 x Quad-Core AMD Opteron Processors (8346 HE @ 1.8Ghz)
64GB DDR2 667Mhz
Fedora 10 x64
Kernel 2.6.28
KVM-82 

KVM Guest Configuration:
32GB Memory
1 to 16 VCPUs
Centos 5.2 x64
Kernel 2.6.28
IDE disk
e1000 NIC

Regards, 
James