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

[Rick Vernam <rickv@hobi.com>]

I'm not so sure there is such a bug - I've been running qemu on AMD 3700 
laptop for years w/o that, or much of any other issue (except once upon a 
time an ACPI issue w/ windows guest causing host cpu to peg 100%).
I run gentoo host + various windows/linux guests.

points of interest may (or may not) be details such as host kernel 
configuration?  qemu version?  qemu options used?  built yourself or 
pre-packaged?
I don't claim to be able to help you solve the problem, but there's not much 
here to work with...

On Tuesday 12 August 2008 11:36:08 am David Barrett wrote:
> 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