[CentOS] using kvm

[Mitch Patenaude]

On Tue, 4 Jan 2011, Jerry Geis wrote:
> >> All -  I am running a virtual windows 7 (pro 64) on centos 5.5 x86_64.
> >> I was hoping to run virtual XP inside windows7 in this configuration.
> >>
> >> I get an error about cannot start virtual XP when I try this.
> >> Do I not have something setup correctly or can I not run a "double"
> >> virtual environment?

In general, it is not possible to nest virtualization environments.
The hypervisor needs to trap certain events/interrupts and reserve
certain instructions to manage the guest OS.  As such, those are not
available to the guest OS, therefore it cannot be a hypervisor itself.

You *might* be able to run an emulator (bochs, qemu, etc) within the
guest OS, but the performance would be something close to abominable.
I'd say you're better off running two guests, one of Win7 and one of
WinXP, and use some other mechanism (virtual network) to let them
communicate.

  -- Mitch