USB Controller Passthrough with VMWare ESXi 5.1

Earlier last year I built myself a VMWare ESXi whitebox computer. VMWare ESXi is a light operating system which allows multiple virtual computers (referred to as virtual machines or VM) to be run inside of one computer (called the host) at the same time. For example, I usually have three VMs running on my box including a FreeNAS file server, Ubuntu, and Windows 8.

One of the features of ESXi (and other hypervisors) is that you can pass through physical devices such as a video card and USB devices into the VMs. That way, you could interact with one of the VMs running inside the host, with a monitor and physical devices much like a real computer. This is great because you can use the host like a real computer, while running other operating systems on it at the same time.

Simplified virtualized computer diagrams — A simplified diagram showing how hardware can be passed through to virtual machines through the hypervisor.

This setup worked well with ESXi 5.0, as long as you had chosen the hardware that supports device passthrough — see my original post for the hardware I am using. As far as I know, any update and patches in the ESXi 5.0 series have working device passthrough.

However, with ESXi 5.1, USB controller passthrough has been broken. On the majority of builds, when you select a USB controller for passthrough, the selection will vanish once you reboot. Or even worse, it will randomly crash the hypervisor.

The only patch of ESXi 5.1 that seems to allow some sort of USB controller passthrough is build 1021289, corresponding to ESXi510-201303001. You can find this patch on the VMWare patch portal, and I have some notes in my previous blog post about updating ESXi. The catch is that the USB controllers will schedule to disable passthrough for themselves upon the next reboot.

esxi-5.1-passthrough-issue — When you enable passthrough devices in the configuration, they will work after you reboot. However, they will be configured to disable themselves after the subsequent reboot.

This wasn’t really a problem for me because I rarely reboot the host machine. Just remember before you shutdown or reboot the host, re-enable the passthrough devices in the DirectPath I/O Configuration screen, and they will work the next time ESXi boots up.

So in short, for reliable device passthrough in VMWare ESXi, stick with the 5.0 series. If you have to upgrade to ESXi 5.1, install the ESXi510-201303001 patch, and remember to re-enable the passthrough devices before rebooting the host. Keep track of this thread on the VMWare Community, as it has been a long running thread documenting issues with device passthrough on ESXi 5.1.