Talk:COMP 3000 Essay 2 2010 Question 9

Group members

• Munther Hussain
• Jonathon Slonosky
• Michael Bingham
• Chris Sullivan
• Pawel Raubic

Group work

• Background concepts: Munther Hussain
• Research problem:
• Contribution:
• Critique:

General discussion

Hey there, this is Munther. The prof said that we should be contacting each other to see whos still on board for the course. So please if you read this, add your name to the list of members above. You can my find my contact info in my profile page by clicking my signature. We shall talk about the details and how we will approach this in the next few days --Hesperus 16:41, 12 November 2010 (UTC)

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Checked in -- JSlonosky

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Pawel has already contacted us so he still in for the course, that makes 3 of us. The other three members, please drop in and add your name. We need to confirm the members today by 1:00 pm. --Hesperus 12:18, 15 November 2010 (UTC)

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Checked in --Mbingham 15:08, 15 November 2010 (UTC)

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Checked in --Smcilroy 17:03, 15 November 2010 (UTC)

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To the person above me (Smcilroy): I can see that you're assigned to group 7 and not this one. So did the prof move you to this group or something ? We haven't confirmed or emailed the prof yet, I will wait until 1:00 pm. --Hesperus 17:22, 15 November 2010 (UTC)

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Alright, so I just emailed the prof the list of members that have checked in so far (the names listed above plus Pawel Raubic), Smcilroy: I still don't know whether you're in this group or not, though I don't see your name listed in the group assignments on the course webpage. To the other members: if you're still interested in doing the course, please drop in here and add your name or even email me, you can find my contact info in my profile page(just click my signature).

Personally speaking, I find the topic of this article (The Turtle Project) to be quite interesting and approachable, in fact we've already been playing with VirtualBox and VMWare and such things, so we should be familiar with some of the concepts the article approaches like nested-virtualization, hypervisors, supervisors, etc, things that we even covered in class and we can in fact test on our machines. I've already started reading the article, hopefully tonight we'll start posting some basic ideas or concepts and talk about the article in general. I will be in tomorrow's tutorial session in the 4th floor in case some of you guys want to get to know one another. --Hesperus 18:43, 15 November 2010 (UTC)

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Yeah, it looks pretty good to me. Unfortunately, I am attending Ozzy Osbourne on the 25th, so I'd like it if we could get ourselves organized early so I can get my part done and not letting it fall on you guys. Not that I would let that happen --JSlonosky 02:51, 16 November 2010 (UTC)

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Why waste your money on that old man ? I'd love to see Halford though, I'm sure he'll do some classic Priest material, haven't checked the new record yet, but the cover looks awful, definitely the worst and most ridiculous cover of the year. Anyways, enough music talk. I think we should get it done at least on 24th, we should leave the last day to do the editing and stuff. I removed Smcilroy from the members list, I think he checked in here by mistake because I can see him in group 7. So far, we're 5, still missing one member. --Hesperus 05:36, 16 November 2010 (UTC)

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Yeah that would be pretty sweet. I figured I might as well see him when I can; Since he is going to be dead soon. How is he not already? Alright well, the other member should show up soon, or I'd guess that we are a group of 5. --JSlonosky 16:37, 16 November 2010 (UTC)

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Hey dudes. I think we need to get going here.. the paper is due in 4 days. I just did the paper intro section (provided the title, authors, research labs, links, etc.). I have read the paper twice so far and will be spending the whole day working on the background concepts and the research problem sections.

I'm still not sure on how we should divide the work and sections among the members, especially regarding the research contribution and critique, I mean those sections should not be based or written from the perspective of one person, we all need to work and discuss those paper concepts together.

If anyone wants to add something, then please add but don't edit or alter the already existing content. Lets try to get as many thoughts/ideas as possible and then we will edit and filter the redundancy later. And lets make sure that we add summary comments to our edits to make it easier to keep track of everything.

Also, we're still missing one member: Shawn Hansen. Its weird because on last Wednesday's lab, the prof told me that he attended the lab and signed his name, so he should still be in the course. --Hesperus 18:07, 21 November 2010 (UTC)

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Yeah man. We really do need to get on this. Not going to ozzy so I got free time now. I am reading it again to refresh my memory of it and will put notes of what I think we can criticize about it and such. What kind of references do you think we will need? Similar papers etc? If you need to a hold of me. Best way is through email. jslonosk@connect.Carleton.ca. And if that is still in our group but doesn't participate, too bad for him--JSlonosky 14:42, 22 November 2010 (UTC)

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The section on the related work has all the things we need to as far as other papers go. Also, I was able to find other research papers that are not mentioned in the paper. I will definitely be adding those paper by tonight. For the time being, I will handle the background concepts. I added a group work section below to keep track of whos doing what. I should get the background concept done hopefully by tonight. If anyone want to help with the other sections that would be great, please add your name to the section you want to handle below.

I added a general paper summary below just to illustrate the general idea behind each section. If anybody wants to add anything, feel free to do so. --Hesperus 18:55, 22 November 2010 (UTC)

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I remember the prof mentioned the most important part of the paper is the Critique so we gotta focus on that altogether not just one person for sure.--Praubic 19:22, 22 November 2010 (UTC)

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Yeah absloutely, I agree. But first, lets pin down the crucial points. And then we can discuss them collectively. If anyone happens to come across what he thinks is good or bad, then you can add it below to the good/bad points. Maybe the group work idea is bad, but I just thought maybe if we each member focuses on a specific part in the beginning, we can maybe have a better overall idea of what the paper is about. --Hesperus 19:42, 22 November 2010 (UTC)

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Ok, another thing I figured is that the paper doesn't directly hint at why nested virtualization is necessary? I posted a link in references and I'l try to research more into the purpose of nested virtualization.--Praubic 19:45, 22 November 2010 (UTC)

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Actually the paper does talk about that. Look at the first two paragraphs in the introduction section of the paper on page 1. But you're right, they don't really elaborate, I think its because its not the purpose or the aim of the paper in the first place. --Hesperus 20:31, 22 November 2010 (UTC)

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The stuff that Michael provided are excellent. That was actually what I was planning on doing. I will start by defining virtualization, hypervisors, computer ring security, the need and uses of nested virtualization, the models, etc. --Hesperus 22:14, 22 November 2010 (UTC)

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So here my question who doing what in the group work and where should I focus my attention to do my part?- Csulliva

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I have posted few things regarding the background concepts on the main page. I will go back and edit it today and talk about other things like: nested virtualization, the need and advantages of NV, the models, the trap and emulate model of x86 machines, computer paging which is discussed in the paper, computer ring security which again they touch on at some point in the paper. I can easily move some of the things I wrote in the theory section to the main page, but I want to consult the prof first on some of those things.

One thing that I'm still unsure of is how far should we go here ? should we provide background on the hardware architecture used by the authors like the x86 family and the VMX chips, or maybe some of the concepts discussed later on in the testing such as optimization, emulation, para-virtualization ?

I will speak and consult the prof today after our lecture. If other members want to help, you guys can start with the related work and see how the content of the paper compares to previous or even current research papers. --Hesperus 08:08, 23 November 2010 (UTC)

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In response to what Michael mentioned above in the background section: we should definitely talk about that, from what I understood, they apply the same model (the trap and emulate) but they provide optimizations and ways to increase the trap calls efficiency between the nested environments, so thats definitely a contribution, but its more of a performance optimization kind of contribution I guess, which is why I mentioned the optimizations in the contribution section below. --Hesperus 08:08, 23 November 2010 (UTC)

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Ok, so for those who didn't attend today's lecture, the prof was nice enough to give us an extension for the paper, the due date now is Dec 2nd. And thats really good, given that some of those concepts require time to sort of formulate. I also asked the prof on the approach that we should follow in terms of presenting the material, and he mentioned that you need to provide enough information for each section to make your follow student understand what the paper is about without them having to actually read the paper or go through it in detail. He also mentioned the need to distill some of the details, if the paper spends a whole page explaining multi-dimensional paging, we should probably explain that in 2 small paragraphs or something.

Also, we should always cite resources. If the resource is a book, we should cite the page number as well. --Hesperus 15:16, 23 November 2010 (UTC)

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Yeah I am really thankful he left us with another week to do it. I am sure we all have at least 3 projects due soon, other than this Essay. I'll type up the stuff that I had highlighted for Tuesday as a break tomorrow. I was going to do it yesterday but he gave us an extension, so I slacked off a bit. I also forgot :/ --JSlonosky 23:43, 24 November 2010 (UTC)

Paper summary

Background Concepts and Other Stuff

EDIT: Just noticed that someone has put their name down to do the background concept stuff, so Munther feel free to use this as a starting point if you like.

The above looks good. I thought id maybe start touching on some of the sections, so let me know what you guys think. Heres what I think would be useful to go over in the Background Concepts section:

• Firstly, nested virtualization. Why we use nested virtualization (paper gives example of XP inside win 7). Maybe going over the trap and emulate model of nested virtualization.
• Some of the terminology of nested virtualization. The difference between guest/host hypervisors (we're already familiar with guest/host OSs), the terminology of L0, ..., Ln with L0 being the bottom hypervisor, etc
• x86 nested virtualization limitations. Single level architecture, guest/host mode, VMX instructions and how to emulate them. Some of this is in section 3.2of the paper.

Again, anything else you guys think we should add would be great.

Commenting some more on the above summary, under the "main contributions" part, do you think we should count the nested VMX virtualization part as a contribution? If we have multiplexing memory and multiplexing I/O as a main contribution, it would seem to make sense to have multiplexing the CPU as well, especially within the limitations of the x86 architecture. Unless they are using someone else's technique for virtualizing these instructions.--Mbingham 21:16, 22 November 2010 (UTC)

Research problem

The paper provides a solution for Nested-virtualization on x86 based computers. Their approach is software-based, meaning that, they're not really altering the underlying architecture, and this is basically the most interesting thing about the paper, since x86 computers don't support nested-virtualization in terms of hardware, but apparently they were able to do it.

The goal of nested virtualization and multiple host hypervisors comes down to efficiency. Example: Virtualization on servers has been rapidly gaining popularity. The next evolution step is to extend a single level of memory management virtualization support to handle nested virtualization, which is critical for high performance. [1]

How does the concept apply to the quickly developing cloud computing?

Cloud user manages his own virtual machine directly through a hypervisor of choice. In addition it provides increased security by hypervicsor-level intrusion detection.

Related work

Comparisons with other related/similar research and work:

Refer to the following website and to the related work section in the paper regarding this section: http://www.spinics.net/lists/kvm/msg43940.html

[This is a forum post by one of the authors of our assigned paper where he talks about more recent research work on virtualization, particularly in his first paragraph, he refers to some more recent research by the VMWare technical support team. He also talks about some of the research papers referred to in our assigned paper.]

Theory (Section 3.1)

Apparently, theres 2 models to applying nested-virtualization:

• Multiple-level architecture support: where every hypervisor handles every other hypervisor running on top of it. For instance, if L0 (host hypervisor) runs L1. If L1 attempts to run L2, then the trap handling and the work needed to be done to allow L1 to instantiate a new VM is handled by L0. More generally, if L2 attempts to created its own VM, then L1 will handle the trap handling and such.

• Single-level architecture support: This is the model supported by the x86 machines. This model is tied into the concept of "Trap and emulate", where every hypervisor tries to emulate the underlying hardware (the VMX chip in the paper implementation) and presents a fake ground for the hypervisor running on top of it (the guest hypervisor) to operate on, letting it think that he's running on the actual hardware. The idea here is that in order for a guest hypervisor to operate and gain hardware-level privileges, it evokes a fault or a trap, this trap or fault is then handled or caught by the main host hypervisor and then inspected to see if its a legitimate or appropriate command or request, if it is, the host gives privilige to the guest, again having it think that its actually running on the main bare-metal hardware.

In this model, everything must go back to the main host hypervisor. Then the host hypervisor forwards the trap and virtualization specification to the above-level involved or responsible. For instance, if L0 runs L1. Then L1 attempts to run L2. Then the command to run L2 goes down to L0 and then L0 forwards this command to L1 again. This is the model we're interested in because this what x86 machines basically follow. Look at figure 1 in the paper for a better understanding of this.

Main contribution

The paper propose two new-developed techniques:

• Multi-dimensional paging (for memory virtualization)
• Multiple-level device management (for I/O virtualization)

Other contributions:

• Micro-optimizations to improve performance.

Implementation

The turtle project has four components that is crucial to its implementation.

• Nested VMX virtualization for nested CPU virtualization
• Multi-dimensional paging for nested MMU virtualization
• Multi-level device assignment for nested I/O virtualization
• Micro-Optimizations to make it go faster

How does the Nest VMX virtualization work: L0(the lowest most hypervisor) runs L1 with VMCS0->1(virtual machine control structure).The VMCS is the fundamental data structure that hypervisor per pars, describing the virtual machine, which is passed along to the CPU to be executed. L1(also a hypervisor) prepares VMCS1->2 to run its own virtual machine which executes vmlaunch. vmlaunch will trap and L0 will have the handle the tape because L1 is running as a virtual machine do to the fact that L0 is using the architectural mod for a hypervisor. So in order to have multiplexing happen by making L2 run as a virtual machine of L1. So L0 merges VMCS's; VMCS0->1 merges with VMCS1->2 to become VMCS0->2(enabling L0 to run L2 directly). L0 will now launch a L2 which cause it to trap. L0 handles the trap itself or will forward it to L1 depending if it L1 virtual machines responsibility to handle. The way it handles a single L2 exit, L1 need to read and write to the VMCS disable interrupts which wouldn't normally be a problem but because it running in guest mode as a virtual machine all the operation trap leading to a signal high level L2 exit or L3 exit causes many exits(more exits less performance). Problem was corrected by making the single exit fast and reduced frequency of exits with multi-dimensional paging. In the end L1 or L0 base on the trap will finish handling it and resumes L2. this Process is repeated over again contentiously.

How Multi-dimensional paging work:

Performance

Two benchmarks were used: kernbench - compiles the linux kernel multiple times. SPECjbb - designed to measure server side [perofmance for Java run-time environments

Overhead for nested virtualization with kernbench is 10.3% and 6.3% for Specjbb. There are two sources of overhead evident in nested conceptualization. First, the transitions between L1 and L2 are slower than the transition in the lower level of the nested design (between L0 and L1). Second the code handling EXITs running on the host hypervisor such as L1 is much slower than the same code in L0.

Critique

The good:

• From what I read so far, the research showed in the paper is probably the first to achieve efficent x86 nested-virtualization without altering the hardware, relying on software-only techniques and mechanisms. They also won the Jay Lepreau best paper award.

• security - being able to run other hypervisors without being detected

• testing, debugging - of hypervisors

The bad:

• lots of exits. to be continued. (anyone whos is interested feel free to take this topic)

References

[1] http://www.haifux.org/lectures/225/ - Nested x86 Virtualization - Muli Ben-Yehuda