Re: Testing nested virtualization

[Daniel Bareiro <daniel-listas@gmx.net>]

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Hi, Alex.

On Saturday, 02 January 2010 14:48:26 +0100,
Alexander Graf wrote:

> >>>> In this guest I'm using Linux 2.6.32, with userspace kvm-85 of
> >>>> backports. For the VM booted within of 'test', I am using a qcow2
> >>>> file. But when connecting via VNC, the boot process is hung in
> >>>> "Press for F12 boot menu". Sometimes it gets to pass this
> >>>> instance and I see the Debian install menu, but while I cross the
> >>>> options, it is hung.

> >>> Also I was trying to use qemu-kvm-0.12.1.1 with to Linux 2.6.32 in
> >>> guest within 'test'. And here it happens something similar.
> >>> Sometimes I get to select the option of the menu of the installer,
> >>> but after boot, the installation is hung again.

> >> Can your host do nested paging? Shadow shadow paging can be a bit
> >> flaky at times :-(.
 
> > Hmmm... is there some way to verify that?
> > 
> > The CPUs model is AMD Athlon 64 X2 Dual Core 3800+. Perhaps some flag
> > related? In such case, these are the available ones in the host:
> > 
> > flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge
> > mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext
> > fxsr_opt rdtscp lm 3dnowext 3dnow rep_good pni cx16 lahf_lm cmp_legacy
> > svm extapic cr8_legacy
> > 
> > 
> > When loading the module with "kvm_amd nested=1", /var/log/messages
> > registers the following thing:
> > 
> > kvm: Nested Virtualization enabled

> With nested paging it would show something like this in dmesg:
> 
> kvm: Nested Paging enabled

Hmmm... dmesg shows just like /var/log/messages:


kvm: Nested Virtualization enabled


"Nested Paging enabled" would have to be a complementary message?
 
> All family 10 AMD CPUs have nested paging (read: quad-core and above).

But this model is dual-Core :-(. That would mean that it cannot do
nested paging?
 
> So I guess you found something going wrong with shadow-shadow paging.
> CC'ing Jörg. He's more into memory management than me :-).

We hope then that Jörg can illuminate a little more to us :-).

Thanks for your reply.

Regards,
Daniel
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