[GSoC 2010][RESEND] Completing Nested VMX

[GSoC 2010][RESEND] Completing Nested VMX

[Mohammed Gamal]

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?

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

Regards,
Mohammed

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

[Luiz Capitulino]

On Mon, 5 Apr 2010 20:34:26 +0200
Mohammed Gamal <m.gamal005@gmail.com> 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?
> 
> And within the scopr of GSoC, what do you think the achievments of
> such a project should be?

 Alex, weren't you involved in nested VMX support too?

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

[Alexander Graf]

On 05.04.2010, at 21:37, Luiz Capitulino wrote:

> On Mon, 5 Apr 2010 20:34:26 +0200
> Mohammed Gamal <m.gamal005@gmail.com> 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?
>> 
>> And within the scopr of GSoC, what do you think the achievments of
>> such a project should be?
> 
> Alex, weren't you involved in nested VMX support too?

Nope, I only did nested SVM. I know rather little about VMX except for the basic principles.

Alex

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

[Mohammed Gamal]

On Mon, Apr 5, 2010 at 9:42 PM, Alexander Graf <agraf@suse.de> wrote:
>
> On 05.04.2010, at 21:37, Luiz Capitulino wrote:
>
>> On Mon, 5 Apr 2010 20:34:26 +0200
>> Mohammed Gamal <m.gamal005@gmail.com> 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?
>>>
>>> And within the scopr of GSoC, what do you think the achievments of
>>> such a project should be?
>>
>> Alex, weren't you involved in nested VMX support too?
>
> Nope, I only did nested SVM. I know rather little about VMX except for the basic principles.
>
> Alex
>
>

Maybe Orit Wasserman or Avi would have some feedback on this?

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

[Avi Kivity]

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.