Category Archives: Work


Sifteo and San Francisco

If you’ve been following me on Twitter you’ve probably noticed I’m not dead yet, despite the extreme silence on this blog lately. Well, possibly I just turned into a really inanely chatty zombie. But either way, I haven’t been cranking out awesome projects like mad. What gives??

First big event: this past July, I moved to San Francisco. Having grown up in the suburbs all my life, I’ve always wanted to live in a big city. So, I decided to pull up roots a bit and make that happen. So far, I feel like it’s one of the best decisions I could have made. If you also happen to live in SF, drop me a line. I’d love to meet, perhaps for an IPA or Trippel at Toronado or a fantastic soy latte at Ritual.

Then, a bit of a career shift. For the past six years, I’ve done a variety of operating systems, graphics, USB, and Bluetooth work at VMware. It’s been awesome, and I had the chance to build some great things there that I still get to use every day when I run VMware Fusion. But it was time for a change. I really wanted to work at a startup, and do something more hardware-focused.

So, very shortly after moving to SF, I got a job with Sifteo, makers of the adorable little gaming cubes that everybody loves. I arrived at the company shortly before their cubes went to market, so I didn’t have much time to influence that product much, but I’ve been having a fantastic time doing future R&D work for them lately. We have some seriously fantastic stuff in store, and I can’t wait until I can share it with everyone.

And finally, as if that were too few New Things, I’m now one week in to a month-long trip to Thailand! I’m loving it so far. I discovered that I totally suck at trip logs, but luckily my travelling companion is a rather awesome amateur photographer, and he’s been keeping a blog at

With any luck, after I get back to the states I’ll have some more time for personal projects. Perhaps I’ll even get a chance to finish something I started.


Announcing vusb-analyzer 1.1

The Virtual USB Analyzer is a graphical tool for analyzing USB sniffer logs. It can do some basic protocol decoding, and it has a graphical timeline view which helps to visualize the latency and concurrency characteristics of USB traffic.

This release only adds a single feature, but it’s one that many people have probably been waiting for: support for Linux’s built-in usbmon sniffer tool.

With usbmon, tracing all USB traffic on your system is as simple as cat’ing text from a sysfs node to a file. It doesn’t have quite as many features as VMware’s low-level capture logs, but for most users (especially users debugging Linux USB drivers) this should be more than sufficient.

If you aren’t familiar with usbmon, the first thing to read is Documentation/usb/usbmon.txt from your kernel sources. That will tell you the basics, including how to capture raw data from the kernel. There are a few other simple front-ends for making this data more human-readable. If you’re using vusb-analyzer, those tools aren’t required. Just save the raw data to a file with a .mon extension, and hand that to vusb-analyzer.

This feature was a patch contributed by Christoph Zimmermann. Without his contribution, I no doubt would have procrastinated this release for many more years 🙂


Graphics in VMware Fusion 3 and Workstation 7

I work on the graphics virtualization team at VMware. The company is about to release two new desktop virtualization products: Fusion 3.0 is in beta, with a release coming tomorrow. Workstation 7.0 has a public release candidate available.

There are a lot of exciting features in these releases, and my team has been working really hard on making the graphics virtualization in these releases the best we can. Our focus with these releases has been introducing a few large architectural changes in our graphics stack:

  • A brand new WDDM graphics driver for Windows 7 and Vista.

This is a complete rewrite, sharing no code with our Windows 2000/XP driver. This has been a monumental undertaking for the team, but the results have been pretty shiny. The architecture is clean and extensible, it’s much easier to understand and debug the driver’s performance, and it gives us a good platform to build on for future guest driver releases. Oh, and it can run 3D games with Aero enabled.

  • A brand new OpenGL driver for Windows guests.

Yes, this release has not one but two brand new drivers in it! The new OpenGL driver is based on Gallium, and it finally brings both major graphics APIs into VMware virtual machines. Both of our new drivers really deserve a blog post all to themselves.

  • We’ve been progressively rearchitecting the host-side infrastructure with a project we call “Better Unity and Multi-mon”.

Whereas previous releases of VMware’s products have implemented multi-monitor support and Unity mode on top of an architecture that was fundamentally designed for a single framebuffer, Fusion’s entire graphics stack has been overhauled in order to natively handle multiple screens, windows, and framebuffers. This architecture is common to all of our products, but so far only Fusion 3.0 has had its entire stack updated. Workstation and ESX still use a blend of new and legacy components.

As an end-user, the effects of our Better Unity and Multi-mon project are relatively subtle. Unity mode now renders much more efficiently, and applications like games and media players will run just as fast in Unity mode as they will in single window or fullscreen mode. Window resizing is smoother. We also have a high-quality GPU accelerated scaler which you can see in action on your VM’s live thumbnails in the VM Library window.

Screen Object

Back in April, I announced the VMware SVGA Device Developer Kit. This is an Open Source (MIT-style license) project which documents the virtual hardware interface that our graphics stack uses, and provides a simple reference driver and some examples. If you’re interested in operating system development, graphics, or virtualization, it can be a handy platform to experiment with, and it’s the best starting point if you’re trying to write a VMware graphics driver for a new operating system.

I’ve been trying to maintain the DDK with an open development process. Instead of periodically dumping code, all development takes place directly in the open repository. The one exception to this policy is for code which doesn’t work on released VMware products, either due to serious bugs or unreleased features.

As part of our architectural improvements for Fusion 3 and Workstation 7, we added a pretty big new feature to the SVGA device: “Screen Object”. Without Screen Object, the device has a single framebuffer with a geometry controlled by a set of registers. Multi-monitor support was faked by using an additional set of registers to carve up a single large rectangular framebuffer into individual monitors. With Screen Object, the guest can create “screens” dynamically, and they don’t necessarily need to be backed by any specific kind of memory.

A Screen is really an opaque non-guest-addressable memory object, just like an SVGA3D surface. If a Surface is analogous to a texture or a backbuffer, a Screen is analogous to a frontbuffer. You can blit between system memory and a Screen, and you can blit from Surface to Screen.

This is a simple concept, but it’s a powerful tool that can be used to implement a variety of different memory management and asynchronous rendering strategies. Last week I checked in a pretty big update to the DDK which includes refdriver support for Screen Objects, and 10 new Screen Object-only examples.

To run the examples, you’ll need Fusion 3 or Workstation 7. You’ll also need to manually enable Screen Object. Like many new features, we haven’t enabled Screen Object by default right away. It is enabled automatically for Vista, Windows Server 2008, Windows 7, and Mac OS X guests, since our drivers on those platforms may take advantage of the new features. For improved portability, it is disabled by default on other guest OS types. You can enable it manually by adding a line to your VMX file:

svga.enableScreenObject = TRUE

As always, the DDK is provided as-is, with no official support from VMware. So please don’t bug our support folks 😉 But I’ll try to answer questions as time permits if you send them to micah at Thanks!


Announcing the VMware SVGA Device Developer Kit

Over the weekend, I finally had time to release another work-related open source project: the VMware SVGA Device Developer Kit. It’s a set of documentation and example code for the virtual graphics card that’s present in all VMware virtual machines. The examples run on the (virtual) bare metal, so it’s a really easy way to experiment with low-level graphics driver programming.


Virtual USB Analyzer

From late 2005 to early 2007, I worked on the USB virtualization stack at VMware. We ran into all sorts of gnarly bugs, many of which were very hard to reproduce or which required access to esoteric or expensive hardware. To help with debugging problems both internally and with customers in the field, we added logging support to our virtual USB stack. Starting with VMware Workstation 5.5, if you set the right hidden config option we’d start dumping the contents of all USB packets to a log. It was a USB sniffer (like USB Snoopy), but built into the virtual hardware.

To make it easier to analyze the resulting logs, I started working on a GUI tool that could navigate through these giant log files. This tool proved to be really useful within our team at VMware, and we’d often ask customers on the beta forums to generate log files that we could analyze. I called this tool vusb-analyzer.

Well, it’s been a while, but I’m proud to now have the opportunity to release vusb-analyzer as open source software under the MIT license. This isn’t just a code dump- I removed the tool from our internal repository today, and all future development will occur in the open, in a Subversion repository on Source Forge.

Currently, vusb-analyzer is most useful for analyzing logs captured by VMware products. Indeed, this is a convenient way to debug USB drivers. You can attach your USB device to VMware Workstation, VMware Fusion, or the free-as-in-beer VMware Player, and it can transparently save a plaintext log of all USB packets that pass through. Debugging a driver in a VM is really convenient, and I find it quite useful, but I understand it’s not for everybody. If you already have a favorite USB sniffer tool, it’s easy to extend vusb-analyzer with a log format plugin so it can read other formats. We already did this once, to add support for the logs generated by our favorite hardware USB analyzers.

I hope vusb-analyzer turns out to be useful for the open source community, particularly to those who are working on Linux device drivers. To get started, visit the project’s web site:

Besides the usual introduction and download links, there is also a detailed tutorial with lots of shiny screenshots 🙂


GPU Virtualization at WIOV ’08

I just got back from the first
USENIX Workshop on I/O Virtualization.

WIOV was an interesting workshop. It was really nice to see what I/O virtualization looks like from a wide range of different viewpoints. There was some good industry perspective from AMD, Intel, Microsoft, and Oracle. There were also a wide range of academic interests represented. Everyone brings not only their own terminology, but their own idea of which problems are particularly hard or useful to solve.

I did feel like a bit of an outsider, though. Nearly the entire workshop was focused on virtualizing storage and networking devices, which are quite a bit different from the devices I work with on a daily basis: mouse, keyboard, graphics, sound, and USB.

Part of this divide is along server vs. desktop lines, but I also feel like it’s in large part due to the wide difference in status of current virtualization approaches for desktop vs. server devices. Most of the current work on networking and storage devices is in improving manageability, or squeezing out that extra 10-20% of performance overhead. This is all already assuming that there are plenty of known virtualization approaches for those devices which are both correct and reasonably performant.

By contrast, current desktop device virtualization is largely neither correct nor performant. Even simple devices like mouse and keyboard must be fudged with heuristic after heuristic to bridge the impedance mismatch between a low-level mouse/keyboard and the high-level input stack abstraction you see at the windowing system or VNC layer. Sound devices are easy to emulate, but to build a truly correct sound device, you would need guarantees that can only be provided by a hard real-time operating system. USB seems on first glance like it could be simple, but there are huge impedance mismatches to be overcome, and even greater challenges in writing a CPU-efficient emulated USB controller.

I feel that graphics virtualization is the biggest unsolved problem in desktop device virtualization, which is why I enjoy my day job as much as I do. But it also means that graphics virtualization is really at a totally different stage than storage or networking virtualization. Nobody has an implementation that is complete or correct, let alone performant. My team at VMware is pushing the envelope, and the technology is already usable for many people- but there’s a huge amount of work left to be done.

I am very greatful to have had the opportunity to present a paper on graphics virtualization at WIOV ’08. Jeremy Sugerman and I co-authored a paper which describes a taxonomy of graphics virtualization approaches, and provides implementation details and analysis for the approach VMware is currently shipping as the DirectX 9.0 virtualization in VMware Fusion and VMware Workstation. This is currently the most detailed publicly available description of the work my team has been doing over the past 4 years. If you’re interested, I encourage you to read the paper closely. It’s really packed with as much information as we could squeeze into 8 pages.

The presentation followed the structure of the paper, but it was weighted heavily toward describing the motivation for GPU virtualization, the reasons why it’s hard, and the characteristics of the different approaches we outline in our taxonomy.

You can get the paper from the official WIOV ’08 site. You can also grab the paper and the presentation slides from my server:

The slides are also on SlideShare, embedded below.


Speaking at USENIX WIOV 2008

Well, this Monday I submitted the final copy of my paper, and yesterday everything was approved. Jeremy Sugerman and I wrote a paper for the USENIX Workshop on I/O Virtualization’s Industrial Practice session: GPU Virtualization on VMware’s Hosted I/O Architecture. We’re on the program for a 15-minute talk at the workshop in San Diego this December.

The paper is a detailed (or as detailed as will fit in 8 pages) description of the GPU virtualization work my team has been doing at VMware for the past couple years. This is the technology that makes it possible to run DirectX 9 applications and games inside your VMware Fusion VM. The paper includes a lot of background information about graphics virtualization, a detailed description of our virtual GPU architecture, and various benchmarks.

Thanks to everyone who helped me by reviewing drafts of the paper. Your feedback has been invaluable.

Update: The paper can now be downloaded in HTML or PDF, and presentation slides are available.


3D Graphics at VMware

Despite all the random posts about helicopters and embedded systems on here, I haven’t really mentioned what I spend most of my time on these days…

I work in the Interactive Devices group at VMware. For people who aren’t familiar with VMware’s products, we do virtualization: software that lets you run multiple virtual computers inside your real computer. It’s good for data center management and consolidation, but I’m most interested in the ways virtualization can be used on the desktop: It’s great for running Windows apps on your Linux box, or running Windows/Linux software on your Mac using Fusion.

And that’s where our team comes in. While much of the company is focused on doing higher-level tools (user interfaces, management software, APIs) or on infrastructure that primarily benefits server products, our team is really in the heart of the virtualization technology that makes VMware tick on the desktop. We virtualize all the random desktop peripherals like the mouse, keyboard, video card, and sound card- but our team’s two big projects are USB and 3D graphics.

I’ve been working at VMware for close to 3 years now. I spent about the first half of that on USB. I did much of the work in implementing USB 2.0, and I did the original port of our OS-specific USB code to Mac OS X prior to the first release of VMware Fusion. I also implemented Isochronous transfer support (for web cams and the like), and did a lot of neat internal testing infrastructure.

I found VMware’s USB project really interesting because it meshed well with my prior experience with embedded systems and creating USB hardware. It was also a good introduction to the challenges in creating virtual hardware devices for a VM, particularly for hardware with such an un-virtualization-friendly architecture.

I still keep tabs on USB at VMware, but lately I’ve been pretty absorbed with our 3D virtualization effort.

For some background: VMware products provide their virtual machines with a “VMware SVGA device”, a made-up video card which provides legacy emulation of VGA and VESA BIOS modes, plus a vendor-specific set of 2D and 3D acceleration features. We provide drivers for this card as part of VMware Tools, and they come with recent versions of Xorg.

Our most recent releases of VMware Workstation and VMware Fusion include 3D acceleration support which is roughly on par with Microsoft DirectX 8.1, but it’s buggy in a lot of ways and it’s missing key features. Needless to say, the 3D team hasn’t been twiddling its thumbs. Our legal department won’t let me disclose exactly how much progress we’ve made or what features we will support in future products, but I can say that I’m very excited about our current work.

3D graphics virtualization is a really complex and interesting problem. Fundamentally what we’re doing is a Direct3D to OpenGL API translator (much like what the Wine project has) but it’s complicated by the fact that we also have to behave like a video card, and we also have to get the data into and out of a Virtual Machine efficiently. All said and done, the actual 3D API translation issues are only part of the story. There are also a lot of interesting resource management and synchronization problems.

It’s a really interesting project and we’re making some great progress, but we also have one big problem:

Our team is tiny. We have a substantial amount of work to do- it’s like writing a major 3D graphics driver (think ATI or NVidia), writing a game engine, and writing a complex interprocess communication system all rolled into one. Right now we have 7 developers on the project, and it feels like we could use 70.

So, if you know anyone who has a passion for 3D graphics, who knows low-level systems programming inside and out, who isn’t afraid of single-stepping through machine code in the debugger: take a look at our job postings (search for OpenGL) or send a resume to micah at vmware dot com.


Random Update

Well, it’s been a while since I’ve updated. Nothing on its own recently has inspired me much to write, but I have some smallish things to mention.

I have a new laptop on the way! My 700 MHz Pentium III with 192MB of RAM was just getting too clunky for day-to-day use. I recently ordered a Thinkpad T43 with 2GHz CPU, 1GB RAM, and SXGA+ 14.1″ display. It shipped Monday, and I can’t wait to start using a Real Computer.

At work, things were stagnating a bit for the past few days. I have three fairly large changes all blocking on code reviews, and no really solid projects in progress. Well, today that changed- I got some new hardware, and began on a really exciting Top Sekret project. If it goes well, you’ll find out eventually.

Life? Not bad at all… I had a really enjoyable three-day weekend. David, Jen, and Kendra are visiting during their spring break, in less than a month. Plans for that week-long adventure are starting to gel, and I can’t wait.

[Update: The Top Sekret project in this post would eventually become VMware Fusion 1.0. I was working on USB at the time, and I did the original port of VMware’s USB stack to Mac OS.]