Re: [Xen-devel] nested virtualizaiton test report for Xen 4.3-RC1

[Pasi Kärkkäinen <pasik@xxxxxx>]

On Thu, Jun 27, 2013 at 12:37:56PM +0100, George Dunlap wrote:
> On Fri, May 10, 2013 at 12:07 PM, Ren, Yongjie <yongjie.ren@xxxxxxxxx> wrote:
> > Hi All,
> > This the a nested virtualization test report for Xen 4.3-RC1 on Intel 
> > hardware. We use Linux 3.9.1 as Dom0.
> > a. Virtual EPT and VMCS shadowing features can work fine.
> > b. Xen, KVM and VMware can basically work on top of L0 Xen.
> > c. 32bit/64bit Linux and Windows are covered as L2 guests.
> 
> Sorry I just saw this -- thanks for the nice enumeration.
> 
> Two questions.  First, I don't see the Win7 "XP compatibility mode" on
> this list -- that would be L0 Xen, L1 Win7, L2 XP.  This seems like
> probably the most likely actual real-world use of nested virt.  Is
> that on your radar at all?
> 
> Secondly, what do you think is the primary use case for Xen-on-Xen (or
> KVM-on-Xen, &c)?  Who would want to use it and why?
> 

I can think of at least two use-cases:

- Xen-on-Xen might be good for testing/debugging the hypervisor.. Much easier 
to crash and debug the virtual Xen rather than physical machine.
- Xen-on-Xen makes it possible to create easy-and-fast-to-clone lab/poc/test 
environments with "full" functionality thanks to virtual vmx and ept..


-- Pasi


> Thanks,
>  -George
> 
> >
> > There are three basic entities in Xen nested virtualization.
> >         L0: Xen (64bit Xen and 64bit Dom0), which is at the bottom of the 
> > nested stack.
> >         L1: Xen or KVM or VMware or VirtualBox  (all in 64bit mode)
> >         L2: Linux or Windows guest, which is at the top of the nested stack.
> > (when saying 'KVM on Xen', I mean L0 hypervisor is Xen and L1 hypervisor is 
> > KVM.)
> >
> > Workable cases: (Pass)
> > 1. virtual EPT and VMCS shadowing feature enabled
> > 2. 64bit Linux/Windows as L2 guest for "Xen on Xen"
> > 3. 64bit Linux guest as L2 guest for "KVM on Xen"
> > 4. L1 KVM and L1 Xen simultaneously running on a L0 Xen
> > 5. L2 guest Save/Restore and local migration for "KVM on Xen"
> > 6. AVX and XSAVE in L2 guest for "KVM on Xen"
> > 7. some workloads (e.g. LTP, Kernel-build, UnixBench) can work fine in 
> > 64bit L2 Linux guest
> > 8. 64bit Linux L2 guest can boot up for "VMware on Xen"
> > 9. 32bit L2 guest (Linux/Windows) booting on "Xen on Xen"  (not use EPT in 
> > L1)
> > 10. 32bit/64bit Windows and 32bit Linux L2 guest booting on "VMware on Xen" 
> >  (not use EPT in L1)
> > N.B. Only if you don't use EPT feature in L1 hypervisor, case #9 and #10 
> > can work fine.
> >
> > Non-workable cases: (Fail)
> > 1. 32bit/64bit Windows L2 guest booting on "KVM on Xen"
> > 2. L2 guest Save/Restore and local migration for "Xen on Xen"
> > 3. Migration "from L0 to L1" for "Xen on Xen"
> > 4. Migration "from L1 to L0" for "Xen on Xen"
> > 5. Migration a L1 Xen/KVM guest with a L2 running in that L1
> > 6. L2 guest booting on "VirtualBox on Xen"
> >
> >
> > Best Regards,
> >      Yongjie (Jay)
> >
> >
> >
> > _______________________________________________
> > Xen-devel mailing list
> > Xen-devel@xxxxxxxxxxxxx
> > http://lists.xen.org/xen-devel
> 
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