Re: [GSoC 2010][RESEND] Completing Nested VMX

[Avi Kivity <avi@redhat.com>]

On 04/05/2010 09:34 PM, Mohammed Gamal wrote:
> Hello All,
> I'm interested in adding nested VMX support to KVM in GSoC 2010 (among
> other things). I see that Orit Wasserman has done some work in this
> area, but it didn't get merged yet. The last patches were a few months
> ago and I have not seen any substantial progress in that front ever
> since.
>
> I wonder whether the previous work can be used as a starting ground
> for any future effort? What is missing from it? What are the current
> limitations of that implementation? And how can it be extended?
>    

The biggest problem of the existing code is maintainablity.  vmx is 
complicated, and nested vmx is much more so.  If it is to be merged, it 
must be in a form that doesn't impact additional work on vmx (i.e. 
unrelated features or optimizations) and that doesn't break each time we 
modify the code.  Other problems are security and correctness.

> And within the scopr of GSoC, what do you think the achievments of
> such a project should be?
>    

A minimal goal would be to merge something that allows running kvm and 
another hypervisor on kvm.  However, I don't think it is realistic for a 
GSoC project; vmx is incredibly complicated, and the bar for merging 
will be set fairly high because of the impact on day-to-day maintenance.

Nested svm took several release cycles to get right (and some bits are 
still missing), and it's much, much simpler than nested vmx.

-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.