[Qemu-devel] AMD 100% CPU bug; patch available?

[David Barrett]

Can anybody confirm that qemu works on an AMD processor with a Linux 
host and Linux guest (ideally Ubuntu 8.04 in both cases) without using 
100% CPU?  (qemu process on the host uses 100% CPU despite all processes 
on the guest being idle.)

Or is there a known bug that qemu with a Ubuntu guest always uses 100% 
CPU on AMD Ubuntu hosts?  If so, is there a patch or workaround for it?

I don't know this for certain, but it's the only pattern I can see: I've 
run qemu on a bunch of laptops and servers over the past 12 months -- 
often with the exact same image and exact same commands -- and some 
hosts see the guest VM use limited CPU, and others a solid 100%.  This 
seems to be the case whether or not -kernel-kqemu is used.

At first I thought it was an Ubuntu/Fedora Core issue, as I was running 
Ubuntu on laptops and FC4 on servers (and I only saw this problem on 
servers).  But I just got a new Ubuntu server and the problem remains.

Now I realize there's another commonality: my servers have been 
AMD-based, whereas laptops were Intel based.  With this theory I looked 
through the user forum and saw a strong correlation between reports of 
100% CPU and AMD processors.

Is this old news or a debunked theory?

Is there some tool like CPUIdle I should be running?  Any suggestions 
for how to start debugging the issue?

Thanks!

-david