recent nested-virtualization publications

recent nested-virtualization publications

[Nadav Har'El]

It appears that recently there is growing interest in nested
virtualization.

A few days ago, VMWare released a technical report, titled "Bounding the
Running Time of Interrupt and Exception Forwarding in Recursive
Virtualization for the x86 Architecture", available at
http://www.vmware.com.mx/files/pdf/partners/academic/hh.pdf
This report discusses why nested virtualization is important, and estimates
the performance of multiple levels of nesting. They show that the interrupt
handling time is exponential in the number of levels, but propose hardware
modifications which could make it linear. Their results are based on
simulations, not on an actual implementation of nested virtualization in
VMWare: They say that "current hardware is not performant enough for real
implementation", and that "The design described in this paper is not in
any VMware shipped product".

As I wrote in a previous email, earlier this month we published our paper
on nested VMX in KVM, "The Turtles Project: Design and Implementation of
Nested Virtualization". The paper was not only accepted to the Usenix
Symposium on Operating Systems Design and Implementation (OSDI), it was
even chosen "Jay Lepreau Best Paper". Among other things, this shows that
the program committee and reviewers found nested virtualization to be an
important research topic.

A few months ago, Olivier Berghmans from Antwerp University published an
MSc thesis titled "Nesting Virtual Machines in Virtualization Test
Framework" in which he, again, explained why nested virtualization is
important, and how it can be done without new hardware or software (e.g.,
one option is to run a software-only hypervisor on a hardware-assited
hypervisor, but he surveys many other options), and compared many
different options.

ScaleMP announced in May "VM on VM" (see http://www.scalemp.com/VMonVM),
a feature which allows to run a hypervisor on top of their underlying
hypervisor. I haven't seen any details published on what exactly they
did, or how.

In April, Nested SVM and Nested VMX patches (for hardware-assisted
virtualization) were also sent to Xen. I am not sure what is the
status of these patches.

I put copies of all above mentioned documents (in case there's
difficulty in finding them), in
	 http://www.math.technion.ac.il/~nyh/nested/

--
Nadav Har'El
nyh@il.ibm.com
+972-4-829-6326

Re: recent nested-virtualization publications

[Joerg Roedel]

On Tue, Oct 26, 2010 at 03:10:58PM +0200, Nadav Har'El wrote:

> I put copies of all above mentioned documents (in case there's
> difficulty in finding them), in
> 	 http://www.math.technion.ac.il/~nyh/nested/

Very interesting. Thanks for the overview on that topic.

	Joerg