Re: bad leakage between virtual machines?

[Tom Horsley <tom.horsley@att.net>]

On Fri, 15 Jan 2010 18:37:57 +0100
Jan Kiszka wrote:

> Tom Horsley wrote:
> > I just submitted this fedora bug with lots of details:
> > 
> > https://bugzilla.redhat.com/show_bug.cgi?id=555788
> > 
> > It sure seems to me like the contents of the debug
> > address trap registers are leaking across virtual machines
> > (at least for opterons on this motherboard :-).
> 
> Are only AMD boxes affected, or did you also test on Intel?

I haven't explicitly tested on Intel, but we did just see a
compile on a guest on the Intel host also get the same
Breakpoint/Trap error out of the blue, so it looks as if it
does happen on intel as well as amd.

I'm going to try on my home system (intel) some more this
evening when I get home.

Some of the symptoms sort of lead me to think it might be
inheriting random leftover DRn registers at the time a
new virtual machine is created since a VM that has problems
seems to keep having problems, and other VMs zip along
with no problems at all.

> 
> > 
> > Anyone seen anything like this before? (I've been
> > having similar problems on this host since it was
> > running xen 3.1 before switching to kvm).
> 
> I still have one debug register oddity on my todo list (that one causes
> an unhandled VM exit), but I'm not aware of such an issue nor do I
> remember any patch between 2.6.31.x and now at the moment that may have
> fixed it. Nevertheless, could you retry with latest kvm kernel or a
> recent kvm-kmod release?

Not sure how to do that - if it isn't in the fedora repos, I'm in
uncharted territory trying to run special kernels :-).

> 
> Jan
>